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Flashcards in Orthopaedics - Oncology Deck (20)
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What is the most commonly occurring benign tumour of bone?

Osteochondroma and giant cell tumour


What is the most common type of malignant bone tumour?

The most common type of malignant tumours are those associated with multiple myeloma and metastatic carcinoma (breast, prostate, lung and bowel being very common). These cancers are more common than primary bone tumours.

Important primary bone tumours are osteosarcoma, chondrosarcoma, and Ewings sarcoma.


What is an osteochondroma? In what age group is it most common?

Osteochondroma is a benign tumour of bone that is most common in males under the age of 25. Macroscopically, the bone growth is covered by a cap of cartilage projecting from the bone surface.

Interestingly, it may actually be a hamartoma (a collection of dysplastic cells) rather than a true neoplasm.


Where are osteochondromas most common? How does it behave?

They tend to occur in the metaphysis of long bones with the lower end of the femur and upper end of the tibia being most common.

Osteochondroma's very rarely progress to chondrosarcoma (a malignant cartilagenous tumour). Malignant transformation is more common in a condition called multiple familial osteochondromatosis - a rare hereditary variant characterised by multiple lesions.


As a general rule, in what age group are benign bone tumours most common?

Generally speaking, benign bone tumours are more common in young adult males. The important exceptions are giant cell tumours and enchondroma's. Giant cell tumours are more common in females and enchondromas have no age or sex specificity.

Osteoma, osteoid osteoma, and osteochondromas are all more common in young men under the age of 25.


What are the features of a giant cell tumour? Do they transform?

Like other examples of giant cell pathology, this tumour is composed of multiple oval or spindle shaped cells intermingled with multinuclear giant cells. Giant cell tumours are more common in the epiphysis of long bones with a peak incidence between the ages of 20-40. They are slightly more common in women.

Although they are benign, giant cell tumours are highly aggressive and tend to recur when resected.


Where are giant cell tumours most commonly found?

About 50% of giant cell tumours occur in the knee.


What are the radiological findings of a giant cell tumour?

Giant cell tumours have a "soap bubble" appearance on x ray.


What are the clinical features of an osteoid osteoma?

This type of tumour is less common than osteochondroma and giant cell tumours.

Osteoid osteoma is a benign tumour of neoplastic proliferations of osteoid (newly formed bone) and fibrous tissue. It is more common in patients under 30 and half of cases occur in the femur or tibia.

Clinically, it presents as pain that is relieve by aspirin but not by rest. Treatment is complete excision of the nidus.


What are the important x-ray features of osteoid osteomas?

Radiologically, the important feature is a tiny radiolucent area called a "nidus". In the diaphysis (main body of the long bone), the nidus is surrounded by dense bone and the cortex is thickened.


What are osteoma's and where are they most commonly found?

Osteoma's are tumours composed of dense, mature bone. They appear more often in the skull and facial skeleton and can even project into the paranasal sinuses. They are slightly more common in men.


What is an osteosarcoma and who does it most commonly affect?

This is THE most common primary malignant tumour of bone (remembering that mestatic disease is the most common malignancy to affect bone). It tends to affect men and boys aged between 10-20 years.

They occur most commonly in the metaphysis of long bones with the proximal portion of the tibia and distal femur being preferred.


What are the important clinical features of osteosarcomas? Where do they spread to?

Clinically, osteosarcomas tend to present as a painful swelling which occasionally causes a pathological fracture. There is a 2-3 fold increase above the upper limit of normal in alkaline phosphatase levels (indicating increased bone turnover).

An important clinical feature of osteosarcomas is early spread to the lung (10% at time of presentation), liver and brain.


What are the classic radiological findings of osteosarcomas?

The expanding lesion lifts the periosteum away from bone creating a Codman triangle. They are often described as having a "sunburst" pattern of growth.


What factors predispose to osteosarcomas?

1) Pagets disease of the bone, fibrous dysplasia, chondroma, osteochondroma

2) Ionizing radiation

3) Bone infarcts

4) Familial retinoblastoma (in these patients surgical cure of the primary occular tumour is often followed by later development of osteosarcoma)


What is chondrosarcoma?

Chondrosarcoma is a malignant cartilagenous tumour. It has a peak incidence in men aged 30 to 60 years. It is virtually unheard of in children.

This tumour may arise as a primary tumour or from transformation of a pre-existing cartilagenous tumour especially multiple familiar osteochondromatosis.


Where are chondrosarcomas most commonly found?

Common sites include the pelvis, spine or scapula, the proximal humerus or proximal femur.


What is a Ewing sarcoma?

This is an extremely anaplastic (poorly differentiated) "small blue cell" malignant tumour which actually has a morphological resemblance to malignant lymphoma. It is virtually indistinguishable from PNET of the soft tissue and the two share some similar features. Both tumours result from 11;22 chromosomal translocation which results in fusion of the EWS1 gene to the FLI-1 gene.


What are the clinical features of Ewing sarcoma?

It occurs most commonly in the long bones, ribs, pelvis and scapula. It has a peak incidence in boys younger than 15 years of age and follows and extremely malignant course with early metastasis but it responds to chemotherapy.

In the early stages, Ewing sarcoma can mimic acute osteomyelitis.


A 15 year old boy presents with a pathological fracture following a minor injury on the football pitch. The area of fracture is surrounded by a large tumour which shows marked pleomorphism, high mitotic activity and extensive cartilagenous differentiation.

The most likely diagnosis is:
a) giant cell tumour
b) osteochondroma
c) chondrosarcoma
d) osteosarcoma
e) Ewing sarcoma

d) Osteosarcoma

This question highlights a very important point: in young patients, bone malignancies showing prominent cartilagenous differentiation are almost always chondroblastic osteosarcomas, rather than chrondrosarcomas. Conventional chrondrosarcoma occurs almost exclusively in elderly patients.