Tumours Flashcards

Question

24) Of the following types of periosteal reaction, select the one most likely to indicate a benign process? a. soap-bubble b. sunray c. hair-on-end d. laminated e. Codman’s triangle

Answer 1

a. soap-bubble Periosteal reactions are usually a radiographic manifestation of underlying bone disease. The term ‘soap bubble’ refers to expansion of the cortex without destruction by a lytic bone lesion. The intact cortex usually indicates a benign process, whereas cortical destruction is associated with malignant or aggressive lesions. Sunray and hair-on-end reactions are spiculated forms of periosteal reaction that occur following periosteal elevation by tumour, with tumour preventing the subperiosteal space from filling with new bone. Laminated or ‘onion-skin’ reaction occurs with both malignant and benign processes and indicates an intermittent or cyclical process. Codman’s triangles are formed by elevation and then destruction of the periosteum. They are usually related to malignant tumours but can also be formed by aggressive benign processes.

Answer 2

c. osteoid osteoma Osteoid osteoma accounts for 12% of benign neoplasms of bone. It is most commonly located in the cortex of long bones (50% in the femur and tibia) with 15% in the spine, typically the pedicle. It rarely exceeds 15 mm in size. Young men are most commonly affected, with pain as the predominant presenting feature due to the extensive inflammatory reaction and vascularity of the lesion. With spinal lesions this results in a painful positional scoliosis, though the majority of patients experience improvement of the pain with salicylates. The lucent central area or nidus represents the underlying pathological process, with the surrounding sclerosis representing reactive inflammatory change in normal bone. Treatment traditionally was surgical curettage, but radiologically guided percutaneous radiofrequency ablation is now used.

Answer 3

c. radiation necrosis Ewing’s sarcoma is a relatively common malignant bone marrow tumour related to, and sharing a common chromosomal translocation with peripheral neuroectodermal tumours. It is a very aggressive tumour thatis expressed in the radiological findings of permeative osteolysis, cortical erosion, periostitis and a soft-tissue mass. It principally affects the lower half of the skeleton, with the most frequent location being metadiaphyseal in the femur, ilium, tibia, humerus, fibula and ribs. Both radio- and chemotherapy are used in treatment. Sclerosis within several months of treatment usually indicates bone healing or disease recurrence/persistence. Radiation-induced osteonecrosis is mainly an effect on the osteoblasts and is dose dependent (deterministic). It may be seen within the mandible within 1 year, but in other sites the latent period is longer and can be a number of years.

Answer 4

a. thickness of the cartilage cap Osteochondromas are the commonest bone tumours and are considered developmental exostoses rather than true neoplasms. They represent 20–50% of benign and 10–15% of all bone tumours. They are made up of cortical and medullary bone and an overlying cartilage cap. The cortex and medulla of the osteochondroma are continuous with the underlying host bone. They are typically orientated away from an adjacent distal joint. Lesions are frequently solitary, but multiple lesions are seen in hereditary multiple exostoses, an autosomal dominant syndrome. Malignant transformation occurs in 1% of solitary lesions and in 3–5% of patients with hereditary multiple exostoses. After skeletal maturity, continued lesion growth, particularly of the cartilage cap, is suggestive of malignant transformation. Although benign lesions may reach 10 cm in size, the cartilage cap should not exceed 1.5 cm after skeletal maturation. Any bone that develops by enchondral ossification may develop an osteochondroma, the long bones of the lower extremity being most frequently affected.

Answer 5

c. paraosteal Osteosarcoma is the second most common primary malignancy of bone after multiple myeloma, accounting for 15% of all primary bone tumours. It usually affects those aged 10–30. Ninety-five per cent are of the primary osseous type and, of these, paraosteal osteosarcoma has the most favourable 5-year survival rate of 80%. Other osteosarcomas of the primary osseous type include periosteal (5-year survival rate 50%) and telangiectatic (less than 20%). Multicentric refers to synchronous osteoblastic osteosarcomas at multiple sites. It occurs exclusively in children aged 5–10, and carries an extremely poor prognosis. The soft-tissue type is rare, representing only 1.2% of all soft-tissue tumours. These lesions are primary soft-tissue tumours with no attachment to bone. Death occurs within 3 years in the majority of cases, tumour size being the major predictor of outcome.

Answer 6

c. bizarre paraosteal osteochondromatous proliferation Bizarre paraosteal osteochondromatous proliferation (also known as Nora’s lesion) is a rare condition usually seen in adults in the third and fourth decades of life. Osteochondroma-like lesions are seen most commonly at the proximal and middle phalanges, followed by the metacarpals and metatarsals. A relationship to trauma has been suggested but not proven. Other locations that may be affected include the long bones (especially those of the upper extremity), skull and jaw. It is thought to be a similar process to that which gives rise to lesions in myositis ossificans, reactive periostitis and subungual exostosis. On plain radiographs, a well-defined bony mass is seen attached to the surface of the parent bone. **Features differentiating this from osteochondroma are the absence of angulation away from the nearby physis and a wide base.**

Answer 7

a. soft-tissue myxoma The association of fibrous dysplasia and soft-tissue myxoma is well established and is commonly termed Mazabraud’s syndrome. The key is identifying the relationship between the bone and soft-tissue pathology, with the osseous features of fibrous dysplasia usually preceding the formation of a soft-tissue mass. The condition is non-familial and more commonly affects women, the thigh being the most common location. Typical MRI appearances are of a well-defined lesion with signal intensity similar to water, and often a fat rind or adjacent muscle high signal on T2W images is seen. Although uncommon, there have been reported cases of malignant change into osteosarcoma.

Answer 8

d. T3 N0 M1a Complete staging of primary bone sarcomas is unusual in that it also incorporates the histological staging once tissue diagnosis via biopsy or surgical resection is available. The local TNM classification is T1 (single lesion less than 8 cm), T2 (single lesion over 8 cm) or T3 (skip lesions of any size). Nodal staging is N0 (no nodes) or N1 (any number of metastatic nodes). Metastatic spread is staged, accordingly, as M0 (no metastases), M1a (metastases to lung) or M1b (any other distant site). Once histology is available, tumours can be staged I–IV.

Answer 9

a. Ewing’s sarcoma Ewing’s sarcoma is the commonest malignant bone tumour in children, and the ribs are involved in 30% of cases in children under 10. It is the commonest malignant chest wall tumour. Neuroblastoma presents in children under 5 as a well-defined, soft-tissue mass that may calcify and erodes/splays the ribs. Hodgkin’s disease presents in young adults, and usually involves bones by secondary involvement with direct invasion of sternum or ribs. Osteomyelitis presents at any age with a shorter history (usually less than 2 weeks), and imaging shows rib destruction with a relatively small mass and loss of tissue planes. Hamartoma of the chest wall presents in the first year of life as an extrapleural mass, causing partial/complete destruction of adjacent ribs. Significant calcification and compression of the adjacent lung occur.

Answer 10

e. ground-glass medulla A ground-glass appearance is characteristic of fibrous dysplasia and is the most useful discriminating factor. Other features of fibrous dysplasia of the skull that can help distinguish it from Paget’s disease are symmetry of distribution, presence of a soft-tissue mass, cyst-like changes, thickness of the cranial cortices, and involvement of the paranasal sinuses, maxilla, sphenoid, orbits and nasal cavity.

Answer 11

a. prostatic metastases The resulting pattern following diffuse uptake of 99mTc-labelled diphosphonates in the axial skeleton, with little or no uptake of tracer in the soft tissues or urinary tract, is frequently referred to as a superscan. When there is little uptake in the limbs, the cause is most likely to be diffuse metastases in the axial skeleton, most commonly prostatic or breast. Uptake in metabolic bone disease is more uniform in appearance, and extends into the distal appendicular skeleton. Intense calvarial uptake disproportionate to that in the remainder of the skeleton may also be seen. The most important factor is to recognize the scan as abnormal in the absence of focal lesions. The lack of renal uptake (absent kidney sign) is a useful discriminator.

Answer 12

d. deep endosteal scalloping Distinction of enchondroma and intramedullary chondrosarcoma in the appendicular skeleton proximal to the metacarpals/-tarsals is difficult radiologically. A series of 187 patients showed that chondrosarcoma was associated with endosteal scalloping, with scalloping involving more than two-thirds of the extent of the lesion being strongly suggestive of malignancy. Other powerful discriminating factors identified as favouring chondrosarcoma were cortical destruction, soft-tissue mass, periosteal reaction, radionuclide uptake at scintigraphy and pain associated with the lesion. Chondrosarcoma also tended to be larger with a mean size of 10 cm compared with 6.7 cm for enchondroma. A ground-glass matrix with arcuate calcification is characteristic of both types of cartilaginous lesion. Multiple lesions may be seen in both malignancy and enchondromatosis (Ollier’s disease).

Answer 13

(b) Aneurysmal bone cyst Of the conditions that typically cause lucent, eccentrically expanded lesions, only GCTs and ABCs have fluid-fluid levels on CT imaging. As GCTs do not reach the articular surface, this is most likely to be an ABC.

Answer 14

(d) Fibrous dysplasia Fibrous dysplasia is the commonest benign rib tumour. Second most common is osteochondroma/bony exostosis but this typically occurs at the costochondral junction. Other benign possibilities include GCT and aneurysmal bone cyst.

Answer 15

(a) Myositis ossificans Myositis ossificans is a form of heterotopic bone formation within skeletal muscle, usually resulting from blunt trauma. Although parosteal osteosarcoma can have similar appearances, myositis ossificans typically has denser calcification in the periphery; osteosarcoma shows the reverse phenomenon, with denser calcification centrally. Juxtacortical chondroma typically scallops the underlying cortex. An osteochondroma is continuous with the underlying bone.

Answer 16

(e) Soft tissue haemangiomas Both conditions describe multiple enchondromas affecting the hands and/or feet, and both tend to be unilateral; neither has a genetic component. Both conditions can lead to shortening of the involved arm/leg, resulting in length discrepancy. Malignant degeneration can be to osteosarcoma (young adults), or chondro/fibrosarcoma (older patients); it is more common in Mafucci's syndrome, but is still seen in 5-30% of cases of Ollier's disease. Maffucci's syndrome describes enchondromas with additional multiple soft tissue haemangiomas, if bilateral there is marked asymmetry.

Answer 17

(e) The CT findings Enchondromas present in a slightly younger age group and are more common in females. They typically affect the bones of the hands and feet and are usually less than 5 cm in size. Although both lesions show matrix mineralisation, this feature is slightly commoner in enchondromas. Other features to favour chondrosarcoma over enchondroma include presentation with a mass, cortical destruction and the presence of a soft tissue mass.

Answer 18

(c) Parosteal osteosarcoma Parosteal osteosarcomas have the best prognosis of all osteosarcomas. If no stalk can be clearly identified they can be distinguished from myositis ossificans by the relative density of the centre of the ossified part of the lesion.

Answer 19

(c) lntraosseous lipoma lntraosseous lipomas are rare bone tumours; they are often asymptomatic and present incidental, but can be associated with pain. The commonest locations are within the proximal femur (Ward's triangle) and in the area of the calcaneus described. In these areas there is a relative paucity of trabecular bone and it is thought that this leads to an 'overshoot' phenomenon during the transition of haematopoietic to fatty marrow, with the resultant formation of the lipoma. Central or ring calcification in a lucent lesion in this location of the calcaneus is said to be pathognomonic of an intraosseous lipoma and allows its distinction from a UBC. If clinical doubt persists MR imaging can be used for further clarification and to confirm the presence of fat.

Answer 20

(b) Matrix calcification is a common plain film feature Osteoblastomas are uncommon primary bone tumours (< 1 %). 90% occur in 2nd - 3rd decades, although cases have been documented up to 72 years. They are histologically similar to osteoid osteoma but less well organised and by definition larger (> 2 cm). The majority (30- 40%) of cases occur in the spine, with a slight predominance for the posterior elements (55%). An expansile lesion in osteoblastoma is not typically associated with malignancy. Scoliosis can occur in both and is typically painful, but occurs more commonly in osteoid osteoma, where the scoliosis results from muscle spasm secondary to the inflammatory mediators produced. Osteoblastomas are not radiosensitive and surgical excision is performed in most cases, however, recurrence is seen in up to 50%.

Answer 21

(b) Caffey's disease The appearances are typical of Caffey's disease, also known as infantile cortical hyperostosis. Scurvy and rickets are unlikely to produce this picture in those < 6 months old.

Answer 22

(c) Osteosarcoma Of the above list, osteosarcoma is the most likely. The periosteal reaction (and wide zone of transition) indicates an aggressive lesion. Ewing's sarcoma is more common in the 1-10 year old age group, and fibrosarcoma in the 30-60 year old age group.

Answer 23

(c) Chondrosarcoma Rings and arcs of calcification indicate a chondroid matrix. Chondrosarcoma is the likeliest primary rib tumour in this age group. Other primary malignant tumours include plasmacytoma and lymphoma.

Answer 24

(b) Chondroblastoma Chondroblastomas almost invariably occur in the epiphyses, and 90% occur in those under 30 years old. Lesions to consider in this location and age group include: infection, chondroblastomas, GCTs and, less commonly, ABCs and eosinophilic granulomas. With regards to the other conditions mentioned: GCTs abut the articular surface; ABCs are almost always expansile; simple bone cysts are not epiphyseal; metastases are unlikely in a 20 year old.

Answer 25

(d) Osteoid osteoma The classical finding is that of a central, usually lucent nidus of less than 1.5 cm in size with varying degrees of surrounding sclerosis. There is often a typical clinical picture which enables differentiation from a Brodie abscess.

Answer 26

(b) Carcinoid Sclerotic metastases are typically the result of: prostate carcinoma, carcinoid, transitional cell carcinoma, breast (mixed), medulloblastoma, colon (occasionally), and lymphoma.

Answer 27

(a) Adamantinoma These are locally aggressive lesions which tend to recur and after several recurrences can metastasize to lungs. The main differential diagnosis for this 'soap-bubble' like appearance is fibrous dysplasia, but this usually presents in a slightly younger age group.

Answer 28

(d) Elastofibroma Elastofibroma is benign tumour forming as a reaction to mechanical friction most commonly seen in the subscapular area. Recent evidence suggests a genetic component. It is bilateral in 25%. Its site, presentation and imaging characteristics are usually typical, however, excision is still performed if there is any doubt with regards to malignant transformation.

Answer 29

(c) Giant cell tumour This is the characteristic patient age and site of GCT, where the unfused physis acts as a barrier to spread of the lesion. After fusion, extension to within 1 cm of the articular surface is the commonest pattern, although transarticular spread has been reported. It can have either a 'soap bubble' like appearance or, as described here, a uniform lytic appearance. 10% present with pathological fractures.

Answer 30

(b) Malignant transformation to osteosarcoma occurs in 1 % Hereditary multiple exostoses (also known as diaphyseal aclasia) is an autosomal dominant condition characterised by multiple exostoses. Malignant transformation to chondrosarcoma occurs in 1-5%.

Answer 31

(b) Champagne glass appearance of the pelvis McCune-Albright syndrome is a form of fibrous dysplasia. It is seen in 10% of cases. Radiologically, it is characterised by a polyostotic, unilateral pattern of involvement. The skull is commonly involved. A champagne glass appearance of the pelvis is seen in achondroplasia.

Answer 32

(a) Myositis ossificans These are the typical findings of myositis ossificans. Although· in the acute stages, it can be confused with other entities, as it matures and calcifies, it can be discriminated from osteosarcomas by the pattern of peripheral calcification and from parosteal sarcomas by the lack of a connecting stalk to the cortex.

Answer 33

(d) Malignant fibrous histiocytoma MFH is the commonest primary malignant soft tissue tumour of later life. It presents as a painless progressively enlarging mass. Calcification is seen in up to 20%. Cortical erosion of adjacent bone is a suggestive feature.

Answer 34

(e) Fibrous dysplasia Other causes include gout, myeloma, osteomyelitis and previous trauma.

Answer 35

(d) Chondroblastoma The main differential diagnosis for epiphyseal lesions would be GCT. However, these typically arise in a slightly older age group and only cross the physis once it has fused. Chondrosarcomas occur in an older age group (median age 45 years) and chondromyxoid fibromas are rare (usually but not exclusively metaphyseal) cartilaginous tumours arising from the cortex.

Answer 36

1. b. Aneurysmal bone cyst Aneurysmal bone cyst is most common in females and 75% occur under 20 years of age. The classic presentation is of pain of relatively acute onset with a rapid increase in severity over 6–12 weeks. Common locations include the spine, with a slight preponderance for the posterior elements, and the metaphysis of long bones – femur, tibia, humerus and fibula. The lesion is usually expansile with thin internal trabeculations giving it the characteristic soap-bubble appearance.

Answer 37

4. d. Osteoid osteoma This most commonly presents in the second and third decades. The male:female ratio is 2.5:1. Classically it presents with increasing pain which is worse at night and often relieved with aspirin. Spinal lesions often lead to painful scoliosis. Almost any site in the body may be affected but the most common regions are the lower limb and spine.

Answer 38

9. d. Ewing’s sarcoma ` Ninety-five per cent present between 4 and 25 years of age. Sixty per cent occur in the long bones, mainly in the metadiaphysis and have a typical moth-eaten destructive appearance on plain film. Metastases to the lung, bone and regional lymph nodes are present in 11–30% of cases at the time of diagnosis.

Answer 39

11. d. Telangiectatic osteosarcoma With the MRI finding described, the most likely explanation is that the lesion is a telangiectatic osteosarcoma. This is a rare type of osteosarcoma with a mean age at presentation of 20 years. The most common site is around the knee (62%). Fluid-fluid levels are also seen in giant cell tumours and aneurysmal bone cysts.

Answer 40

22. c. Bronchial carcinoid The most likely from the above list is a bronchial carcinoid. In men the most likely cause would be prostate. All other conditions are likely to produce lytic metastases than sclerotic.

Answer 41

28. a. Osteochondroma The description is classic for an osteochondroma or osteocartilagenous exostosis. These lesions are the most common benign growths of the skeleton, are usually found incidentally and are usually asymptomatic unless complications arise. Complications include fracture, vascular compromise, bursa formation and malignant transformation into chondrosarcoma.

Answer 42

38. d. Enchondroma This lesion is most likely to be an enchondroma. This is a benign cartilaginous growth in the medullary cavity and is usually asymptomatic. It most commonly occurs in the small bones of the hands and wrist but may also occur in the proximal humerus and proximal femur. Epidermoid inclusion cysts are usually in the distal phalangeal tuft and there is often a history of trauma. A bone cyst would be unusual in the phalanges.

Answer 43

39. c. Enchondroma The most common location of these benign lesions is the tubular bones of the wrist and hands, and they are usually asymptomatic and therefore diagnosed incidentally. Of the other lesions mentioned, ABC, simple bone cyst and fibrous dysplasia are rare in the hands. An epidermoid inclusion cyst is most likely to occur at the distal phalanx.

Answer 44

41. c. Myositis ossificans Often there is no distinct history of trauma, although this is the most common cause. It usually occurs in the large muscles of the extremities and in the early stages it can be difficult to distinguish from soft-tissue sarcomas. It is, however, separate from bone, unlike parosteal sarcoma and post-traumatic periostitis. This is a self-limiting condition, most commonly occurring in young athletic adults, with resorption occurring in approximately one year.

Answer 45

42. a. Malignant fibrous histiocytoma Soft-tissue malignant fibrous histiocytoma is the most common primary malignant softtissue tumour of later adulthood. It is most commonly seen in the lower extremities. It has a metastatic rate of 42% and most commonly metastasises to the lung. Osseous malignant fibrous histiocytoma presents as a painful, tender, rapidly enlarging mass and most commonly arises in the metaphysis of long bones.

Answer 46

53. d. Fibrous dysplasia The most common site of monostotic fibrous dysplasia is the ribs, followed by proximal femur and craniofacial bones. Three-quarters of cases present before age 30. Other benign lesions causing a ‘hot’ on bone scan include Paget’s disease, brown tumours, aneurysmal bone cysts, osteoid osteoma and chondroblastoma. Acute fractures are not usually ‘hot’ until after the first 24–48 hours.

Answer 47

55. d. Chondromyxoid fibroma This is most commonly seen in the second and third decades and the most common site is the long bones, most often the proximal tibia and distal femur. Non-ossifying fibroma is usually asymptomatic. The appearances of a chondroblastoma would be similar but this would most likely be epiphyseal in location and usually presents in a slightly younger age group.

Answer 48

58. b. Intra-osseous lipoma The calcaneum is a common location for an intra-osseous lipoma. They do, however, also occur in the extremities, skull and mandible. There is no periosteal reaction unless there is an associated fracture. Imaging features would be similar to those of a unicameral bone cyst. They are often asymptomatic but can present with localised bone pain.

Answer 49

B Carcinoma of the breast

Answer 50

D Chondrosarcoma

Answer 51

C New areas of high signal on T2w images

Answer 52

C Metastatic lung cancer Skeletal metastases tend to involve the axial rather than appendicular skeleton, reflecting their predilection for bones containing red marrow. Metastases from bronchial carcinoma account for half of all peripheral metastases.

Answer 53

B Diaphyseal location

Answer 54

E Osteosarcoma The appearances are highly aggressive, and characteristic of osteosarcoma. The tumour matrix indicates a tumour of osseous rather than cartilaginous origin, malcing chondrosarcoma highly unlikely.

Answer 55

D Isotope bone scan, CT chest with MRI Tlw and T2w sagittal, axial, coronal sequences of the femur The typical imaging algorithm for children suspected of a primary bone malignancy includes plain radiograph, MRI to cover the entire bone involved by the lesion, bone scintigraphy to look for skeletal metastases and a CT chest for pulmonary metastases.

Answer 56

D Osteoblastoma The differential diagnoses for a lesion within the posterior elements of a vertebral body include osteoid osteoma, osteoblastoma and an aneurysmal bone cyst.

Answer 57

D Ewing's sarcoma Infection and Langerhans cell histiocytosis (LCH) should be considered in the differential diagnosis of a permeative bone lesion in a child. Askin tumour is a rare primitive neuroectodermal rumour of the chest wall in children.

Answer 58

D McCune-Albright McCune-Albright syndrome is characterised by polyostotic fibrous dysplasia, cafe-au-lait spots and endocrine disturbance (most commonly precocious puberty in girls). The rare association of polyostotic fibrous dysplasia and soft tissue mxyomas is Mazabraud's syndrome.

Answer 59

E Metastatic prostate cancer

Answer 60

C Multiple osteochondromas

Answer 61

A Aneurysmal bone cyst

Answer 62

C Periosteal reaction Outside the hands and feet, chondrosarcoma is five times more common than enchondroma.

Answer 63

D Osteoid osteoma

Answer 64

A Chondroblastoma

Answer 65

C Giant cell tumour

Answer 66

3. E. Fibrous dysplasia. The clue here is the cafe-au-lait spots, which are seen in McCune–Albright syndrome (unilateral polyostotic fibrous dysplasia, precocious puberty, and cafe-au-lait spots). Osteomyelitis is unlikely because of the normal inflammatory markers, lack of systemic symptoms, and lack of periosteal reaction. Aneurysmal bone cyst and GCTs are possibilities (the former may even complicate fibrous dysplasia). Chondroblastoma is an epiphyseal lesion.

Answer 67

5. C. Osteoblastoma. Osteoblastoma is similar both clinically and histologically to osteoid osteoma, but there are some differences that aid in distinguishing these two entities. Clinically osteoblastoma is typically less painful than osteoid osteoma and does not respond as well to salicylates. An osteoblastoma in the neural arch of the spine is more likely to cause neurological signs, as these lesions are typically larger and more expansile than osteoid osteoma. The lucent nidus seen in osteoid osteoma is usually less than 1.5–2 cm in size, whereas the nidus in osteoblastoma is usually larger than 2 cm at diagnosis and has less surrounding sclerosis. The nidus may or may not have a calcific focus within, in both these diagnoses. The appearance described in the question is the subgroup of osteoblastoma that has similar features to osteoid osteoma. Other appearances on imaging of osteoblastoma include an expansile lesion with multiple small calcifications and a peripheral sclerotic rim or, more rarely, an aggressive appearance with osseous expansion, bone destruction, infiltrating soft tissue, and intermixed matrix calcification. An enostosis (or bone island) may be giant (greater than 2 cm), but should be well defined and densely sclerotic. It is possible a bone abscess could cause a lytic lesion with surrounding sclerosis, but the patient is systemically well, making infection less likely. A bone abscess is also unlikely to be as expansile as the lesion described. Intracortical haemangioma is a very rare diagnosis, usually within the cortex of a long bone, such as the tibia. On CT there is a hypoattenuating lesion, with spotty internal calcification or a ‘wire-netting’ appearance.

Answer 68

6. B. Giant cell tumour (GCT). This is the classical description and location of a GCT. They occur age 20–40 years, in the long bones and occasionally the sacrum and pelvis. They are lucent, eccentric, and expansile but do not usually produce sclerosis and produce a periosteal reaction in less than a third of patients. They may have a multiloculated appearance. They originate in the metaphysis but extend to the subchondral surface in the skeletally mature. MRI often reveals fluid–fluid levels and some low signal on T2WI due to haemosiderin or collagen deposition. The major differential diagnosis is an aneurysmal bone cyst (ABC), but this classically has a sclerotic margin and usually occurs under 30 years of age (75% occur before the age of 20 years). Fibrous dysplasia would usually present at a younger age in the metaphysis with extension into the diaphysis; a trabeculated/ground-glass appearance is typical with a thick sclerotic margin and endosteal scalloping. Metastasis would be relatively rare at this age and there is no mention of a primary tumour. Osteosarcoma would have a more aggressive appearance with a wide zone of transition, periosteal reaction, cortical destruction, and soft tissue extension.

Answer 69

8. D. Arrange MRI, CT chest, and IBS. The lesion described is probably an osteosarcoma. Ewing’s sarcoma is high on the differential diagnosis, but is less often found in the metaphysis and usually has a soft-tissue component. Osteosarcomas commonly arise from the metaphysis (only 2–11% arise from the diaphysis). They are most common in the distal femur followed by the proximal tibia. If osteoid matrix is present on plain film, osteosarcoma is the diagnosis until proven otherwise. The appropriate action would be to refer to a regional orthopaedic centre for discussion at a multidisciplinary meeting with imaging followed by biopsy or surgery as thought appropriate. An MRI is used to evaluate local extent, the CT chest and IBS to search for pulmonary and bony metastases, respectively. Surgery is often performed after repeat imaging following the administration of neoadjuvant chemotherapy, when the oedema surrounding the tumour is less pronounced. The findings are not particularly suspicious for NAI (option A). It is not safe to assume the appearances are caused by osteomyelitis and in any case more urgent investigation would be required to confirm such a diagnosis. A CT of the area might be useful but involves ionizing radiation, which MRI avoids; the MIBG scan would be appropriate for neuroblastoma, which is unlikely in this age group (90% occur before the age of 5) (option C). A metastasis is very unlikely in this age group.

Answer 70

23. D. Chondroblastoma. These are radiolucent lesions that typically occupy the epiphysis of long bones in younger people, usually before skeletal maturity. They tend to be less than 4 cm in size, with approximately threequarters having a sclerotic border and one-third a calcified matrix seen on plain radiographs. Chondromyxoid fibromas are rare benign tumours occurring in predominantly the second and third decades of life. They characteristically have sclerotic margins and appear lobulated or ‘bubbly’. They usually arise in the metaphysis of long bones with occasional diaphyseal extension. GCTs tend to occur in young adulthood following skeletal maturity. Patients usually present with pain. The lesion is purely lytic, typically with well-defined, but non-sclerotic, margins. When present in long bones, the lesions are typically metaphyseal, extending across a fused epiphysis to a subarticular location. Periosteal reaction is atypical, but expansile remodelling, cortical penetration, and soft-tissue extension may be seen.

Answer 71

28. D. Intraosseus lipoma. This is usually asymptomatic and discovered as an incidental finding in adults between 30 and 60 years. The calcaneus is the most common site for intraosseus lipoma, accounting for approximately 32% of cases. The key radiographic features are as described. The central dystrophic calcification seen in approximately 62% of cases is considered pathognomic. The major differential diagnosis of this lesion is a simple bone cyst, although this would not contain central calcification. Unlike bone cysts elsewhere, it is seen at this site into adulthood. Also within the differential diagnosis is a pseudolesion within the calcaneus, caused by a relative paucity of trabecular bone at the same location. Again, central calcification would not be a feature in this phenomenon. Enchondroma is typically a well-defined osteolytic lesion with central calcification, but it usually has a predilection for tubular bones and would be exceedingly rare in the calcaneus. The described appearances are not typical for bone infarct.

Answer 72

29. C. Osteosarcoma. Telangiectatic variety of osteosarcoma shows fluid–fluid levels, as does malignant fibrous histiocytoma or any necrotic bone tumour. Telangiectatic osteosarcoma is highly vascular and contains necrotic tissue and blood, with tumour located only along periphery and septa. MRI will reveal enhancing nodularity in latter locations; this will be absent in ABC or GCT. In addition, the plain film findings include bone expansion and cortical breakthrough. Unlike the other lesions, osteoblastoma does not demonstrate fluid–fluid levels on MRI; it is more common in the posterior elements of the spine than in the long bones. ABC, GCT, and chondroblastoma have a narrower zone of transition on plain film than telangiectatic osteosarcoma. GCT is subarticular. Chondroblastoma is epiphyseal. Other benign causes of fluid–fluid levels include simple bone cysts and fibrous dysplasia.

Answer 73

43. B. Aneurysmal bone cyst. ABC accounts for approximately 5% of primary rib lesions, excluding myeloma. The radiological findings and age described in the question are classical for this lesion. Approximately 75% of patients are <20 years of age. The key findings on MRI are the fluid–fluid levels due to the settling of degraded blood products within the cysts. Fluid–fluid levels may also be a feature of other lesions, including GCT and chondroblastoma, but the thin, well-defined margins of an ABC should help to distinguish it from other lesions, particularly in this young age group. Fibrous dysplasia is the most common benign rib lesion. The radiographic appearances are variable, but may show unilateral fusiform enlargement and deformity with cortical thickening and increased trabeculation of one or more ribs. The matrix may appear lytic, may demonstrate a ground-glass appearance, or rarely be sclerotic. Amorphous or irregular calcifications may be seen within the lesion on CT, and MRI shows low to intermediate signal on T1WI and variable T2WI signal. Enchondromas more typically arise in the anterior cartilaginous portion of the rib. Radiographs reveal a lobulated, well-demarcated osteolytic lesion that demonstrates mild expansion and well-defined, sclerotic margins. There is typically matrix calcification and CT is more sensitive at detecting this when the calcification is subtle. MRI shows T2WI hyperintense foci that appear to coalesce with one another and reflect the high fluid content of hyaline cartilage. Chondroblastoma of a rib is reported in the literature, but would be exceedingly rare and typically occurs in the epiphyses of long bones. Cystic haemangiomatosis is a rare disease of disseminated multifocal haemangiomatous or lymphangiomatous lesions in the skeleton and is usually an incidental asymptomatic finding.

Answer 74

57. C. Pattern of ossification in the lesion. The pattern of ossification is likely to be the most helpful. In post-traumatic myositis ossificans, the ossification occurs classically first at the periphery, whereas in parosteal osteosarcoma, the ossification is diffuse, but predominantly central. Periosteal reaction is typically absent in both these lesions and both lesions may contain lucent areas on plain radiograph. A lucent cleft between the mass and the bony cortex, representing periosteum, is characteristic in parosteal osteosarcoma, but frequently is not seen as the tumour envelops bone. A thick lucent zone separating myositis ossificans from an adjacent bony cortex is typical, but may not be seen on plain radiograph if the lesion is immediately juxta-cortical.

Answer 75

58. B. Chondrosarcoma. The findings describe development of chondrosarcoma in an area of Paget’s disease. While osteosarcoma is more common than either malignant fibrous histiocytoma or chondrosarcoma in Paget’s disease, the ‘ring-and-arc’ calcification in the vignette indicates chondroid rather than osteoid calcification. Sarcomatous transformation in Paget’s is rare, occurring in approximately 1% of cases, but should be suspected if there is new focal pain or swelling. Such lesions, even osteosarcomas, are usually lucent. Periosteal reaction is often absent due to the rapidity of bone destruction. Other complications of Paget’s disease include those related to osseous weakening (deformity and fracture), arthritis, neurological entrapment, and both benign and malignant GCT. Chondroblastoma may have internal chondroid calcification (60%) but is a well-defined, benign, lucent lesion with a sclerotic rim occurring in the epiphyses of children and young adults. Bronchial carcinoid metastases are usually purely osteoblastic (i.e. sclerotic, not lucent).

Answer 76

62. E. None of the above. The correct answer is to do nothing. This is the classical description of a non-ossifying fibroma (NOF). These and fibrous cortical defects are common in children and adolescents, and are usually a painless, incidental finding. They are eccentric, well-defined, cortically-based lesions with marginal sclerosis. They can be expansile. They are most common in the femur and tibia. Fibrous cortical defects measure less than 2 cm whereas NOFs are larger. They routinely heal by sclerosis and disappear. An IBS can show uptake during healing and a CT scan can show apparent cortical breakthrough. Thus the correct management is to do nothing. If there are atypical features, such as pain or periostitis, then additional investigation is indicated.

Answer 77

66. A. Dysplasia epihysealis hemimelica (Trevor disease). This is an uncommon developmental disorder relating to the formation of an osteochondromatype lesion at the epiphyses of usually a single lower extremity. The epiphyses most commonly involved are those on either side of the knee or ankle. Typically it is only the medial or lateral side of the epiphyses affected (medial:lateral 2:1). The disease is usually recognized at a young age because of an antalgic gait, palpable mass, varus or valgus deformity, or limb length discrepancy.

Answer 78

67. D. Diaphyseal aclasia. The description is classic for multiple hereditary osteochondromas/exostoses, also known as diaphyseal aclasia. Osteochondromas are the result of displaced growth plate cartilage, which causes lateral bone growth from the metaphysis. They typically point away from the epiphysis. There is continuity of the normal marrow, cortex, and periosteum between the exostosis and the host bone. The cartilage cap, which is the source of growth, may have some chondoid matrix, but the appearance is otherwise of a deformed but normal bone. They are normally found in the extremities, with 36% around the knee. Their growth normally ceases at skeletal maturity. Symptoms are related to pressure effects on adjacent neural or vascular structures. Less than 1% of solitary osteochondromas undergo malignant transformation to chondrosarcoma. Findings that should alert to this are destruction of exostosis bone, destruction of matrix in the cartilage cap, irregular or thick (>2 cm in adults, >3 cm in children) cap, or growth of the cap after skeletal maturity. Multiple hereditary osteochondromatosis is an uncommon autosomal dominant condition. Patients present with multiple osteochondromas, which cause short stature. The elbow and wrist joints are often deformed. There is a higher risk of malignant transformation than in solitary osteochondromas, probably 2–5%. Ollier disease is the presence of multiple enchondromas and Mafucci syndrome requires, in addition, multiple soft-tissue haemangiomas. Morquio and Hunter syndromes are mucopolysaccharidoses, with their own musculoskeletal abnormalities, which often make an appearance in exams.

Answer 79

Answer B: Precocious puberty The imaging features are typical of fibrous dysplasia. Fibrous dysplasia, multiple cafe an laic spots and endocrine disorder such as precocious puberty and hyperthyroidism are seen in McCune-Albright syndrome.

Answer 80

8 Answer D: Monostotic Fibrous dysplasia is a skeletal developmental anomaly of bone forming mesenchyme, which manifests as a defect in osteoblastic differentiation and maturation. Almost any bone can be affected. Monostotic is found in 70-80%. Polyostotic is found in 20-30% and can be associated with endocrine dysfunction and cafe an laic spots in 10%. Craniofacial is rarer (10-25% of monostotic, 50% of polyostotic). The familial form is rare.

Answer 81

9 Answer C: Likely aggressive processes Periosteum is composed of two layers, outer fibrous and inner cellular, which has potential for osteoblastic potential. It is more active in childhood and therefore is visualised earlier in children. Periosteal reaction represents either new bone formation or periosteal elevation. The different types of periosteal reaction are: lamellated, solid, speculated, sunburst or hair on end, Codman's triangle. Tumours presenting with speculated, sunburst, disorganised periosteal reaction or Codman's triangle are likely to represent aggressive processes.

Answer 82

14 Answer B: No need for specific treatment, spontaneous resolution is likely Non-ossifying fibromas are also known as fibroxanthoma, fibrous medullary defect and several other synonyms. They are found in up to 40% of children less than two years old. They are generally painless and found in shafts of long bones, mostly lower limb particularly around the knee. They tend to be eccentric within the metaphysis, mostly in the medulla. Multiple lesions have several associations; Neurofibromatosis, fibrous dysplasia, Jaffe-Campanacci syndrome. They tend to be aligned along the axis of the long bone and measure around 2 cm in length. If they are more than 3.3 cm and occupy more than half of the bone diameter, they should be observed. Mostly, these lesions spontaneously resolve.

Answer 83

15 Answer B: Aneurysmal bone cyst Aneurysmal bone cysts are benign expansile lytic lesions containing thin-walled cystic cavities filled with chronic blood products. They present with pain, increasing in severity over 6-12 weeks. The peak age of presentation is 16 years.

Answer 84

36 Answer A: Osteoblastoma Osteoblastomas are clinically and histologically similar to osteoid osteoma with a nidus as a characteristic feature. Enchondromas often have multiple lytic lesions, but there is no nidus. A giant cell tumour is a trabeculated bone lesion. Fibrous dysplasia would be a possibility but the description is classical for an osteoblastoma and fibrous dysplasia more frequently affects the proximal femur.

Answer 85

38 Answer C: Chondroblastoma Chondroblastomas usually occur from 5-20 years and are almost exclusively epiphyseal. Osteosarcomas and non-ossifying fibromas are usually metaphyseal. Lymphoma and Ewing sarcomas are usually diaphyseal.

Answer 86

40 Answer C: Lymphoma Lymphoma of bone is more commonly non-Hodgkin's lymphoma and is predominantly diaphyseal. None of the other lesions are classically diaphyseal nor would they explain his constitutional symptoms.

Answer 87

42 Answer E: Giant cell tumour Giant cell tumours are seen in skeletally mature patients. They are epiphyseal/ metaphyseal, most common in the distal femur and do not cause surrounding sclerosis. Desmoplastic fibromas are osteolytic and metaphyseal but usually have well-defined sclerotic margins. Aneurysmal bone cysts do occur in this age but are metaphyseal and one would expect to see fluid levels within the cystic spaces on MRI. Metastatic breast deposits are generally diaphyseal and rare in this age group. Enchondromas are diaphyseal and have matrix mineralisation.

Answer 88

43 Answer A: Wide resection and reconstruction with allograft Allograft resection is the treatment of choice for a large giant cell tumour causing destruction. A wide resection is preferred as a marginal resection is associated with a high recurrence rate. Chemotherapy has no role in the management of this tumour.

Answer 89

44 Answer C: Osteosarcoma Osteosarcoma is a high-grade intramedullary tumour. It has high signal on T2 W MRI due to replacement of the normal bone marrow and foci of high signal on T1 W MRI because of central haemorrhage. An osteoid osteoma would not have significant periosteal reaction. Osteochondroma is painless with no periosteal reaction. Chondromyxoid fibroma occurs in the third or fourth decade. It is a lucent lesion with a sclerotic rim. Chondrosarcoma is unlikely in this age group, usually present over 40 years of age.

Answer 90

45 Answer B: Chondroblastoma Chondroblastoma typically occur in this age group and are epiphyseal, welldefined lucencies with a thin sclerotic rim. Osteosarcoma, fibrosarcoma and clear cell chondrosarcoma would be expected to have more aggressive features. Osteomas occur in the elderly population and tend to be sclerotic

Answer 91

45 Answer D: Enchondromatosis Enchondromatosis, or Oilier disease, is a non-hereditary failure of cartilage ossification. It can involve the long bones, causing leg or arm shortening, or the tubular bones of the hands and feet, resulting in deformity.

Answer 92

46 Answer A: Osteosarcoma Osteosarcomas are the most common and aggressive primary bone tumours. Despite the potential of arising in any bone, the majority arise in the metaphyseal growth plates of long bones. Other sites are the pelvis and jaw. The peak incidence is in the second and third decades but there is a second peak in the seventh and eighth decades, chiefly as a result of malignant transformation in Paget's disease.

Answer 93

47 Answer E: Chondromyxoid fibroma The proximal tibial metaphysis is a classic location for a chondromyxoid fibroma which is always benign, hence there is a lack of periosteal reaction and softtissue involvement. Aneurysmal bone cysts do occur in the metaphysis; usually a thinned cortex and fluid-fluid levels are visible.

Answer 94

48 Answer C: Percutaneous radiofrequency ablation Percutaneous RFA is the treatment of choice for osteoid osteoma and primary success rates of up to 90% are reported. With secondary recurrence, repeat RFA leads to an even higher success rate approaching 100%. Chemotherapy and irradiation are not indicated in the treatment of these tumours. Resection, curettage, cryotherapy, bone grafting and prosthetic replacement are invasive with a greater risk of incomplete excision.

Answer 95

48 Answer A: Several `ground-glass' medullary lesions within the proximal femur with endosteal scalloping The girl has McCune-Albright syndrome, which consists of at least two out of the triad of. polyostotic fibrous dysplasia, cafe an laic spots and endocrinopathy including precocious puberty. The cafe an laic spots in McCune-Albright syndrome tend to be fewer in number and more prominent than the smooth-edged lesions seen in neurofibromatosis. The other radiographic findings listed above are all seen in neurofibromatosis.

Answer 96

49 Answer A: Fibrous dysplasia The popcorn-shaped calcifications are cartilage-producing nodules, which are typical of fibrous dysplasia.

Answer 97

51 Answer D: Simple bone cyst Simple bone cysts often have prominent fluid levels. They commonly present in the second decade and are slightly expansile. Aneurysmal bone cysts have more marked expansion with fluid-fluid levels and tend to occur in an older age group. Fibrous dysplasia is unlikely as it is not an entirely lytic lesion. Giant cell tumour is lytic but often has septations. With brown tumours there is osteoclastic activity due to hyperparathyroidism, so there would usually be osteopenia.

Answer 98

52 Answer A: Ewing sarcoma With Ewing sarcoma `onion skinning' reflects the periodic activity of the sarcoma interspersed with quiescent periods. Brodie's abscess is high on the differential given the systemic upset, but usually has a lytic area with surrounding sclerosis. Trauma is not likely due to the insidious onset. Neuroblastoma typically occurs under the age of five.

Answer 99

54 Answer E: Thinned cortex with mild expansion Simple bone cysts are fluid-filled lesions of unknown aetiology. They are most common in males in the first two decades of life and are metaphyseal lesions which migrate into the diaphysis over time. They may have thin internal septae and a thin sclerotic rim is often present.

Answer 100

55 Answer D: Non-Hodgkin's lymphoma It is very rare for Hodgkin's disease to present in bone and most intraosseous lymphomas are of the non-Hodgkin's type.

Answer 101

56 Answer C: Osteosarcoma Osteosarcoma is an aggressive lesion that can be mixed lytic/sclerotic in appearance and is common at this age and site. Granulocytic sarcoma occurs in patients with leukaemia or other myeloproliferative disorder but is rarely sclerotic. Ewing sarcoma has a moth-eaten appearance and is usually lytic. Aneurysmal bone cysts are not aggressive. Osteoid osteoma has a nidus and no bony destruction.

Answer 102

56 Answer E: Ewing's sarcoma Ewing's sarcoma is the most common bone tumour in children. The lesions are characteristically illdefined mottled `moth eaten' areas of bone destruction with a periosteal reaction that has an `onion skin' appearance. There is usually an associated soft-tissue mass. Osteomyelitis can have similar appearances but usually a shorter history. In eosinophilic granuloma there is a solid periosteal reaction. Osteosarcoma does not cause a lamellar periosteal reaction and frequently has ossification in the soft tissues.

Answer 103

57 Answer B: Osteochondroma Diaphyseal aclasis is the condition of multiple hereditary osteochondromas. It is an autosomal dominant disorder in which multiple osteochondromas are seen throughout the skeleton, preferentiallyaffecting the long bones. It is associated with short stature and asymmetrical growth leading to deformities.

Answer 104

61 Answer E: Geographic bone destruction with a prominent sclerotic rim No periosteal reaction is present unless there is a fracture. Internal septation is common and there is often thinning of the overlying cortex

Answer 105

61 Answer D: Lymphoma The term ivory vertebra describes single or multiple very dense vertebrae and all the options listed are causes. Paget's disease and haemangiomas show coarse reticulation and some expansion. Low grade infections are associated with endplate destruction, disc narrowing and paraspinal masses. Sclerotic metastases generally do not show expansion but a history of underlying malignancy is often available and there may be evidence of metastatic disease elsewhere.

Answer 106

62 Answer B: 10-20 years Chondroblastomas present as a well-defined lucency usually in the femur, proximal humerus or proximal tibia. Internal calcification is visible in 60% and there is usually florid marrow oedema on MRI.

Answer 107

63 Answer E: Pathologic fracture Malignant degeneration is rare, particularly in solitary peripheral lesions. It is more common with multiple lesions and in more central lesions. Unless it occurs no systemic symptoms occur.

Answer 108

65 Answer D: 1 Male: 2 Female Most bone tumours either have an even sex distribution or are more common in men except Ewing's, aneurismal bone cysts, haemangiomas and giant cell tumours.

Answer 109

66 Answer D: Well-defined cortical lesion with no periosteal reaction Brown tumours occur in hyperparathyroidism and are most common in the primary form. They are also known as osteoclastomas due to parathyroid hormone-stimulated osteoclastic activity. These tumours are eccentric/cortical and are usually solitary.

Answer 110

8 Answer A: Ivory osteoma Ivory osteomas are benign hamartomas of the bone, which are relatively common. They may be associated with other conditions such as Gardener's syndrome. They most commonly occur in the frontal and ethmoid sinuses and may cause obstruction of the sinus ostium. Ivory osteomas are dense areas of compact bone and are well-defined sclerotic bone on CT and low signal on T1-weighted imaging.

Answer 111

12 Answer E: Myositis ossificans This is also known as heterotopic ossification, pseudomalignant tumour of soft tissue and extraosseous localised non-neoplastic bone and cartilage formation. It is a benign solitary selflimiting ossifying soft tissue mass typically occurring within skeletal muscle. Direct trauma is the cause in 75%. The pathology is of a lesion surrounded by compressed fibrous connective tissue and surrounded by atrophic skeletal muscle. The symptoms include pain, tenderness and soft-tissue mass. It has a progressive natural history where it resolves spontaneously, which is reflected in its plain film and MR characteristics.

Answer 112

23 Answer A: Simple bone cyst Simple bone cysts or unicameral bone cysts are most frequently found in the metaphyses of long tubular bones, particularly the proximal humerus, femur and tibia. Fracture is a common complication with the fractured piece of cortex falling to the dependent part of the cyst, the `fallen fragment sign', described above.

Answer 113

36 Answer D: Aneurysmal bone cyst The absence of periosteal reaction and presence of intact cortex make Ewing sarcoma, osteosarcoma or chondrosarcoma unlikely. Fibrous dysplasia is possible but the appearance and location would be atypical. The major differential is a giant cell tumour.

Answer 114

37 Answer D: Ewing sarcoma Ewing sarcoma is commonest in this age group and in a diaphyseal location. Neuroblastoma microscopically does contain small blue cells but typically locates in the adrenal gland of children. Medulloblastoma is composed of small blue cells but typically is found in posterior fossa of children. Osteoblastoma is essentially a large osteoid osteoma. Chondroblastomas are epiphyseal tumours.

Answer 115

39 Answer D: Prostate Prostate cancer is well-known for causing osteoblastic metastases. Breast and lung cancer produce mixed lytic and sclerotic metastases. Kidney and thyroid cancers are usually purely lytic.

Answer 116

40 Answer C: Chondroblastoma The patella is considered an epiphyseal equivalent and hence the same differential applies. Osteosarcomas, osteochondromas and non-ossifying fibromas are metaphyseal lesions. Adamantinomas are diaphyseal.

Answer 117

41 Answer B: Aneurysmal bone cyst The appearance of fluid-fluid levels on MRI is characteristic and the appearance given on plain film is typical.

Answer 118

42 Answer B: Biopsy, `extended' curettage and packing with follow-up X-rays A biopsy is usually performed to confirm the diagnosis and exclude malignancy. Extended curettage is then performed to reduce the risk of recurrence (approx 30%).

Answer 119

43 Answer E: Diaphyseal

Answer 120

44 Answer D: Wide resection and chemotherapy Wide surgical margins and limb-sparing resection combined with chemotherapy is the most successful regime. Pre- and post-operative chemotherapy significantly improves outcome.

Answer 121

45 Answer A: Chest X-ray Lung metastases are the most common metastases from sarcomas, including osteogenic sarcomas. He may also need a CT but of the available options a CXR is the best initial test.

Answer 122

46 Answer C: Chondrosarcoma Chondrosarcoma generally occurs in adults over the age of 60 and the proximal humerus is a common location. `Popcorn' calcification is a typical radiological sign. Chondroblastoma occurs in a much younger patient population (10-30 years) and typically has a sclerotic border.

Answer 123

47 Answer B: Osteoblastoma Osteoblastoma, in contrast to many other benign lesions, are frequently associated with an extracortical mass.

Answer 124

48 Answer E: Osteoid osteoma This is a typical description of an osteoid osteoma with a central nidus.

Answer 125

49 Answer E: McCune-Albright syndrome McCune-Albright syndrome is the triad of fibrous dysplasia, cafe an laic spots and endocrine dysfunction. Bone lesions in fibrous dysplasia typically have a'ground- glass' appearance. Hand- Schuller-Christian disease is the triad of exophthalmos, diabetes insipidus and lytic skull lesions. In Gardner's syndrome there are multiple neoplasms of bone and intestinal polyps. Letterer-Siwe disease is a severe form of histiocytosis X.

Answer 126

50 Answer A: Fibrous dysplasia Fibrous dysplasia typically has a ground-glass appearance, a thick sclerotic border and often presents as a result of a pathological fracture.

Answer 127

51 Answer C: Ewing sarcoma The intermediate signal on T2 is due to the presence of hypercellular tumour combined, which suggests extensive soft-tissue disease, a characteristic feature of Ewing sarcoma. Osteomyelitis can mimic changes of an aggressive bone tumour but is not the most likely diagnosis here. Lymphoma tends to affect older children. Chondroblastoma does occur in this age group but arises in the epiphysis and has a sclerotic rim.

Answer 128

52 Answer E: Giant cell tumour These are typical findings of a GCT and the age of the patient is also typical. Aneurysmal bone cysts tend to cause more expansion and to be more diaphyseal. Unicameral bone cyst (also known as simple bone cyst), can be mildly expansile but not multiloculated.

Answer 129

56 Answer C: Giant cell tumour Giant cell tumours are metaphyseal lesions that extend to the articular surface. They are most common in the third and fourth decades of life. The low signal intensity on Ti- and T2-weighted images seen with giant cell tumours is due to haemosiderin deposition. All the other diagnoses have high signal intensity on T2 -weighted images.

Answer 130

53 Answer D: Sacrum When Ewing's affects the spine the sacrum is most commonly affected, followed by the lumbar, thoracic and cervical regions in that order.

Answer 131

54 Answer A: Enchondroma The description is typical. The risk of malignant degeneration in solitary peripheral enchondromas is very small.

Answer 132

55 Answer B: Osteosarcoma The most common site for osteosarcoma is the distal femur. Pain is worse with activity and with a high ALP the patient is more likely to have lung metastases.

Answer 133

58 Answer E: Osteoid osteoma The appearance of a central nidus with surrounding sclerosis is common. Osteoblastoma tends to have irregular margins and is larger (2-10 cm). Chronic sclerosing osteomyelitis is also usually irregular with more bone destruction and periosteal reaction although it is possible to mistake a sequestrum for the nidus.

Answer 134

58 Answer C: Aneurysmal bone cyst An aneurysmal bone cyst is very vascular hence exhibits increased uptake in the blood-pool phase. A simple bone cyst has no uptake. An enostosis has no uptake.

Answer 135

59 Answer B: Lymphoma of bone lymphoma is most likely to have this appearance; it is relatively slow growing. Multiple myeloma is lucent but has no expansion. A sarcoma would also be possible but is not listed.

Answer 136

60 Answer D: Chondroblastoma Chondroblastoma is a benign cartilaginous tumour that normally occurs before closure of the growth plates and is characteristically found in the epiphyses of long bones, particularly the femur and tibia. Patients tend to present with a long history of pain. They may become locally aggressive and rarely metastasise.

Answer 137

61 Answer C: 30-40 years Haemangiopericytoma is a rare tumour that usually occurs in the soft tissue of the thigh, pelvis or retroperitoneum and presents as a painless slow-growing mass. They may show locally aggressive behaviour.

Answer 138

62 Answer B: Normal surrounding bone, rings and arcs within lesion

Answer 139

62 Answer B: Osteosarcoma Osteosarcoma usually presents with a one- to two-month history of painful swelling and often with associated fever. Ewing's sarcoma rarely contains any calcification.

Answer 140

70 Answer A: None Enostoses are benign incidental findings that may increase slowly or decrease in size. It could be significant if at a critical load-bearing region but at 7 mm it is unlikely to be clinically relevant in the ilium.

Answer 141

5 Answer A: Cartilaginous rest Cartilaginous rests are round radiolucencies, caused by displaced cartilage in the bone. An enchondroma is a benign cartilaginous lesion. Enchondromatosis, also known as Ollier's disease, is due to derangement of cartilaginous growth, leading to migration of cartilaginous rests from the epiphysis to the metaphysis, where proliferation occurs. It is usually diagnosed in childhood and, in addition to abnormal growth, it is associated with juvenile granulosa cell tumours of the ovary. The main complication is sarcomatous transformation, which is more common in axial rather than appendicular enchondromas. Maffucci's syndrome is similar except that it also involves haemangiomas and lymphangiomas.

Answer 142

6 Answer B: Radionuclide whole body bone scan Skeletal survey is more appropriate for multiple myeloma screening. Some literature states PSA<20 does not warrant a bone scan although centres vary in their practice. CT of the whole spine is unnecessary, although a targeted study can be useful if there is doubt. Similarly MR can be performed but this should be targeted at areas flagged up by a bone scan. 3-phase bone scans are used for targeted regions to assess for loosening and infection.

Answer 143

11 Answer D: Fibrous dysplasia Fibrous dysplasia is a pathology of unknown aetiology and usually occurs before 30 years of age. It involves increased proliferation of woven bone within the medullary cavity that cannot develop to lamellar bone and is most commonly monostotic but can be polyostotic. Bone expansion resulting in facial deformity can occur and malignant transformation has been described (<0.5 %). If the skull base is affected the neural foraminae can become stenosed. The radiological appearances are diverse dependent on the degree of fibrous tissue produced. A CT scan characteristically reveals an expansile bony lesion that displays groundglass density. The bony expansion can be identified as a result of widening of the medullary space with the cortex remaining intact. MRI usually shows a low signal intensity on both Ti- and T2-weighted images and intense enhancement following administration of contrast. Polyostotic fibrous dysplasia is a feature of Albright's syndrome (cutaneous pigmentation, fibrous dysplasia and precocious puberty). Paget's disease produces mixed lyric and sclerotic lesions, is more common in males, primarily involves the vertebrae and skull and occurs later in life. Ossifying fibromas are more focal, displaying discrete zones of osseous or fibrous tissue and behaving more aggressively.

Answer 144

15 Answer B: Fibrous dysplasia There are at least 10 causes but the four most common are: osteomalacia, fibrous dysplasia, osteogenesis imperfecta, Paget's. Pseudofractures are the same as Looser lines or osteoid seams, and are insufficiency fractures and non-union. They occur at sites of mechanical stress such as where vessels enter bone. They tend to be bilateral and symmetric at right angles to the bone margin. The pathognomonic sign is a 2-3 mm stripe of lucency at right angles to the cortex (osteoid seam).

Answer 145

Answer A: Paget's disease Paget's disease presents with a mixed hearing loss due to fixation of the stapes in the oval window, giving a conductive deficit and loss of cochlear bone density, producing a sensorineural deficit. Both monostotic and polyostotic fibrous dysplasia normally present as an incidental finding in a young age group with the classical ground-glass appearance on CT. The clinical picture does not fit with a potential diagnosis of osteomyelitis. Typical CT appearances of ossifying fibroma are of a cortically based lyric lesion with a thick bony rim in a young patient.

Answer 146

35 Answer B: Chondromyxoid fibroma Chondromyxoid fibroma is a rare benign cartilaginous tumour that presents with pain. It is usually found in the metaphysis of the long bones, most commonly in the proximal tibia. There is no associated periosteal reaction unless it is fractured.

Answer 147

36 Answer E: Prostate carcinoma Elevated alkaline phosphatase in elderly men must raise the suspicion of bony metastases from prostate carcinoma, which is the commonest cause of sclerotic metastases.

Answer 148

37 Answer B: Chondrosarcoma Both chondrosarcoma and osteosarcoma commonly present with paraneoplastic hyperglycaemia (85% of cases with central chondrosarcoma, 25% of osteosarcoma) but the patient's age and the site are more typical for a chondrosarcoma.

Answer 149

38 Answer D: Giant cell tumour Giant cell tumours are almost invariably epiphyseal although they may extend to involve the metaphysis. They occur almost exclusively in those with closed epiphyses and are eccentric with a non-sclerotic margin.

Answer 150

38 Answer C: Ewing's sarcoma Forty per cent of Ewing's sarcoma are found in the flat bones and usually have a disproportionately large soft-tissue mass. They have a large intrathoracic component and a minimal extrathoracic component.

Answer 151

39 Answer A: Osteitis fibrosa cystica Osteitis fibrosa cystica is caused by an excess of PTH causing increased osteoclastic resorption of bone. It is seen in people with hyperparathyroidism and can present with headaches and bone pain. Fibrous dysplasia, osteochondroma, Paget's disease of bone and giant cell tumour are not associated with disorders of calcium metabolism.

Answer 152

40 Answer B: Well-defined lucent lesion with sclerotic rim in the metaphysis Chondromyxoid fibromas generally occur between the ages of 10 and 30 years. Internal calcification is uncommon.

Answer 153

42 Answer A: Epiphyseal Giant cell tumours are usually epiphyseal in a sub-articular location but may extend from the epiphysis to involve the metaphysis. Ninety-seven per cent occur after closure of the epiphyses.

Answer 154

42 Answer A: Osteoblastoma Approximately half of osteoblastomas are found in the spine, most of which arise in the posterior elements. They typically present with painful scoliosis, worse at night.

Answer 155

43 Answer E: Osteosarcoma Osteosarcoma may rarely arise in Paget's disease through malignant degeneration. Sclerotic metastases are probably more common even in someone known to have Paget's but are usually multifocal and would rarely involve only one part of one bone.

Answer 156

44 Answer E: 10-20% Osteosarcoma has a very poor prognosis once metastases are present.

Answer 157

45 Answer C: Osteoid osteoma Osteoid osteoma is a benign bone tumour composed of osteoid and woven bone that usually affects young individuals. They are small tumours (less than 2 cm in diameter) with a central nidus in which prostaglandin E2 is elevated. This has been suggested to be the cause of the pain experienced and explains the typical history of relief with salicylates.

Answer 158

47 Answer E: Osteoid osteoma The femoral neck is the most common location for osteoid osteomas.

Answer 159

48 Answer B: Giant cell tumour Giant cell tumours are typically epiphyseal and the `soap bubble' appearance is characteristic. More destruction would be expected with the other options.

Answer 160

49 Answer D: Osteoid osteoma Osteoid osteoma has a typical double-density sign of a nidus with surrounding activity due to the reactive sclerosis. With a stress fracture of the femoral neck it is unusual to see the double-density sign. Brodie's abscess usually has a more uniform pattern of radiotracer uptake. A simple bone cyst has no uptake on a bone scan.

Answer 161

50 Answer A: Mazabraud's syndrome Mazabraud's syndrome is the rare association of fibrous dysplasia with intramuscular myxoma and is an important differential for a soft-tissue mass with lytic bone lesions.

Answer 162

51 Answer B: Chondrosarcoma Chondrosarcoma tends to occur in those over 40 and the median age at presentation is 45 years. Giant cell tumour has a peak incidence in the third and fourth decades, and has a female preponderance. Osteosarcoma is most often seen in the first to third decades of life, although there is a second peak after the age of 60 due to Paget's disease. Aneurysmal bone cyst is most commonly present in the second and third decades and osteoid osteoma in the first three decades.

Answer 163

52 Answer A: Femur The most common location is the femur followed by the ilium, tibia, humerus, fibula sacrum and ribs in that order.

Answer 164

53 Answer D: Metaphyseal and diaphyseal Approximately two-thirds of Ewing sarcomas affect long bones and half of these are centred in themetadiaphysis

Answer 165

54 Answer D: Osteogenic sarcoma Osteogenic sarcoma is the most common primary malignant bone tumour. It classically affects adolescents with a second peak in incidence after the age of 60 due to Paget's disease. The typical presentation is with pain of several weeks' duration, commonly with activity. The most common bones involved are the femur and tibia with the majority of lesions occurring around the knee. An important differential is osteomyelitis.

Answer 166

55 Answer D: Simple bone cyst

Answer 167

56 Answer D: Chondroblastoma Chondroblastomas are usually spherical, well-defined lesions in an epiphyseal location and with a fine sclerotic margin. Florid marrow oedema surrounding the lesion is also a typical feature. Aneurysmal bone cysts have a low signal rim on both T1- and T2 -weighted MRI images but bone marrow oedema is not typical. Giant cell tumours are rare in children and their margins are not sclerotic. Chondrosarcomas are epiphyseal but rare in this age group.

Answer 168

57 Answer C: Metaphysis Enchondromas are metaphyseal, although they may affect the epiphysis after closure of the growth plate.

Answer 169

57 Answer A: A well-demarcated low-attenuation lesion a few millimetres in size, surrounded by an area of high attenuation Osteoid osteoma is a common benign bone tumour. Its commonest location is within the cortex of long bones. It characteristically presents with pain that is worse at night and is relieved by non-steroidal anti-inflammatory drugs. On plain radiographs it is a small (<1.5 cm) lytic lesion, which is surrounded by reactive sclerosis. The nidus may not be visible on plain radiographs due to the density of the surrounding sclerosis. CT shows the nidus in these cases. Osteoblastoma is a rare benign tumour that can undergo malignant transformation. It is similar histologically to osteoid osteoma. It has a nidus of >1.5 cm that ranges from lytic to densely sclerotic in appearance.

Answer 170

58 Answer C: Alpha feta protein Sacrococcygeal teratoma is the most common solid tumour occurring in the newborn and alpha feta protein is raised in malignant teratomas. It is more common in girls and is associated with other congenital anomalies such as spinal dysraphism, sacral agenesis, hydronephrosis, imperforate anus and gastroschisis. Sacrococcygeal teratomas are typically mixed cystic/solid and on MRI they are heterogeneous with high signal on T1-weighted images. The older the child is at presentation the more likely the tumour is to be malignant.

Answer 171

59 Answer A: Expansile, lytic lesion Thyroid and renal cell carcinoma metastases are nearly always osteolytic. Other causes of lytic metastases include melanoma, lung and breast carcinomas. The most common causes of sclerotic metastases are prostatic, breast, colonic and bladder carcinomas in addition to melanoma and soft tissue sarcomas.

Answer 172

62 Answer C: Metacarpals The majority occur in the small tubular bones of the hand.

Answer 173

63 Answer B: 10-30 years Three-quarters will be within this range

Answer 174

3. (c) Intraosseous lipoma This is an expansile, non-aggressive lesion usually seen in metaphyses. It may contain a focal area of dystrophic calcification within (secondary to fat necrosis). On MRI, the lesion returns fat signal on all sequences (high signal on T1 and T2, and low signal on STIR).

Answer 175

4. (a) Unicameral bone cyst This is usually asymptomatic unless fractured. The lesion usually is 2–3 cm in size, usually in the metaphysis, with its long axis parallel to the long axis of the bone. There may be endosteal scalloping of the bone and a ‘fallen-fragment sign’ (if fractured, centrally dislodged fracture fragment falls into a dependent position in the cyst).

Answer 176

5. (d) Ewing’s sarcoma with fracture For a simple fracture with haematoma, this case has presented too early for a periosteal reaction. Neuroblastoma metastasis could be considered in a child less than 5 years old, and lymphoma should be considered in patients over 30 years age. Osteomyelitis could have been possible if there had been a previous history of localised pain, fever etc.

Answer 177

9. (e) Osteoid osteoma This typically presents as a small lytic lesion with central mineralisation surrounded by reactive sclerotic area. On bone scans, the central nidus shows intense uptake surrounded by region of lesser activity (double density sign). MRI demonstrates bone oedema pattern and typically relieved with aspirin. Stress fractures are transverse and linear. Ewing’s sarcoma and infection must be considered if soft tissue involvement is seen on MRI.

Answer 178

10. (b) Giant cell tumour Typical features on radiograph are a lytic, eccentric, expansile, subarticular lesion with ‘soap bubble’ appearance (fluid–fluid level on MRI). Benign fibrous histiocytoma and telangiectatic osteosarcoma can also show fluid– fluid levels but are metaphyseal lesions not extending to the subarticular surface. A simple bone cyst is unilocular and situated away from the articular surface.

Answer 179

12. (a) Dermoid They are usually an incidental finding. They have a characteristic appearance of a central lucent area with sclerotic margins.

Answer 180

13. (b) Non-ossifying fibroma or a fibrous cortical defect These benign lesions typically present like this. On MRI, they appear as low signal on T1 and T2 images due to hypocellular fibrous tissue within. Chondromyxoid fibromas show a bulging cortex and geographical bone destruction with calcifications and septations. On MRI they are hyperintense on T2. Intraosseous ganglion is hyperintense on T2. Aneurysmal bone cysts show fluid–fluid levels and are heterogenously hyperintense on MRI.

Answer 181

17. (b) Maffucci’s syndrome This diagnosis is a combination of multiple enchondromatosis and soft tissue haemangiomas. Hand and foot involvement is common and severe. The soft tissue calcifications are phleboliths from haemangiomas. In Ollier’s disease, there is absence of haemangioma and phleboliths.

Answer 182

19. (b) Chondroblastoma This is the most common neoplasm seen in the apophysis/epiphysis of skeletally immature patients. These are typical imaging features, showing a lytic lesion with sclerotic margins and calcifications in the matrix. There is surrounding marrow and soft tissue oedema. MRI overestimates the extent. The tumour is almost always benign but may become locally aggressive.

Answer 183

31. (d) Parosteal lipoma These are benign tumours of adipose tissue which are intimately related to the periosteum. They often contain bony excrescences that may resemble osteochondroma but, unlike osteochondroma, they do not communicate with the medullary cavity of parent bone. MRI is diagnostic, confirming the juxtacortical benign nature of the fatty lesion and non-communication of the bony lesion with the medulla of the adjacent bone.

Answer 184

32. (a) Osteochondroma The best diagnostic feature of osteochondroma is continuity of the bony cortex and medulla with the parent bone.

Answer 185

33. (b) Enchondroma Radiographic features are typical and diagnostic. A bone infarct appears as a serpiginous area with sclerotic margins and no endosteal scalloping. Chondrosarcoma shows periosteal reaction and an associated soft tissue mass.

Answer 186

34. (b) Osteoblastoma Also called giant osteoid osteoma when measuring > 2 cm. Osteoid osteoma are < 2 cm, have a predilection for the axial skeleton and usually respond to salicylates. Osteosarcomas show cortical destruction, mineralised matrix and soft tissue mass. Aneurysmal bone cysts show fluid–fluid levels and no matrix calcification.

Answer 187

35. (b) Osteoma The best diagnostic clue is the densely sclerotic, well-defined lesion attached to the parent bone. Latent lesions show no tracer uptake.

Answer 188

44. (a) Ewing’s sarcoma More than 50% of cases are seen in long bones. They are common in the metadiaphyseal region and most common in the 5- to 10-year age group. Often presenting similarly to osteomyelitis. MRI is extremely useful in determining the extent of the tumour, which is low on T1, high on T2 and STIR and enhances with contrast.

Answer 189

47. (b) Fibrous dysplasia CT appearances are typical showing increased volume of bone with ‘ground-glass’ appearance.

Answer 190

Answer: (a) Correct (b) Not correct (c) Not correct (d) Not correct (e) Not correct Explanation: Nocturnal pain is a feature of long bone osteoid osteoma and not of intra-articular lesions. It is also less responsive to NSAIDs. Extensivereactive sclerosis surrounding the nidusis a feature of long bone lesion and not of intra-articular lesion. Nidus is often overlooked on radiographs. MRI is more sensitive than CT in detecting the nidus, however CT is more specific. MRI is sensitive as it is highly sensitive in demonstrating perilesional edema.

Answer 191

Answer: (a) Correct (b) Correct (c) Not correct (d) Not correct (e) Not correct Explanation: Most common location of GCT is around knee joint (50%-65%) with distal femur accounting for 23%-30% cases. Proximal humerus accounts for 4-8% of the cases of GCT. Spinal GCT primarily affects the vertebral bodies with extension into the posterior elements. Vertebral body collapse is a frequent finding. Periosteal reaction is uncommon seen on radiograph only in 10-30% cases. Cortical penetration is however seen in 33-50% cases with associated soft tissue mass.

Answer 192

Answers: (a) Not correct (b) Not correct (c) Not correct (d) Correct (e) Not correct Explanation: About 60% of Ewing tumors arise in long bones, most common site is metadiaphysis of femur. About 40% arise in flat bones especially in pelvis, particularly in patients over 20 years age. Calcification is rare in Ewing’s tumor of bone. It typically presents with an onion skin periosteal reaction on radiograph. Majority of giant cell tumors occur in patients following fusion of the epiphysis. Thus usually occur after 18-20 years of age. They have a narrow zone of transition and usually abut the articular margin. Parosteal osteosarcomas occur in an older age group than the periosteal type with 50% occurring after 30 years of age.

Answer 193

Answers: (a) Correct (b) Correct (c) Correct (d) Not correct (e) Correct Explanation: In osteosarcoma, metastatic spread is heterogeneous, as bones lack a lymphatic system. The lungs are the most frequent size, although bones may be involved. Lymphadenopathy occurs late in the disease and is a poor prognostic sign.

Answer 194

Answers: (a) Not correct (b) Correct (c) Not correct (d) Correct (e) Not correct Explanation: Diaphyseal aclasia is an autosomal dominant disorder presenting between 2 to 10 years of age. The exostoses arise from the metaphysis of long bones and point away from the joint. Risk of malignant transformation to chondrosarcoma is less than 5 %.

Answer 195

Answers: (a) Not correct (b) Not correct (c) Correct (d) Not correct (e) Correct Explanation: Lesions which outgrow their blood supply appear photopenic on bone scintigraphy. Small percentage of prostatic metastases can be entirely lytic. ‘Halo’ of high signal around a lesion on T2WI is highly suggestive of metastases.

Answer 196

Answers: (a) Correct (b) Correct (c) Not correct (d) Correct (e) Correct Explanation: Enchondromas are a relatively common benign medullary cartilaginous neoplasm, usually found in children or young adults which can lead to pathological fractures or undergo malignant degeneration. Mostly they are an incidental finding with benign imaging features. Calcification especially chondroid type is common finding.

Answer 197

Answers: (a) Correct (b) Not correct (c) Not correct (d) Not correct (e) Correct Explanation: Majority of Ewing sarcoma are located in diaphysis of the humerus, femur, tibia and fibula. Epiphysis is a rare location. In the first two decades lesions are predominantly located in long bones. After that time lesions in flat bones are more usual. Ewing is an aggressive tumor with permeative or moth eaten appearance on radiograph with lamellated, onion skin or spiculated periosteal reaction.

Answer 198

Answers: (a) Correct (b) Not correct (c) Correct (d) Correct (e) Correct Explanation: Aneurysmal bone cysts are benign expansile tumour like lesion. Periosteal reaction is not seen until associated with a fracture.

Answer 199

Answers: (a) Not correct (b) Correct (c) Correct (d) Correct (e) Correct Explanation: Fibrous dysplasia typically presents before the age of 30 years. The most common sites of involvement of the ribs, cranial, facial bones and femur and tibia.

Tumours Flashcards

(223 cards)