7. Chondroid tumours

Question 1

Types of chondroid tumours

Answer 1

1. Chondroma
2. Osteochondroma (exostosis)
3. Chondrosarcoma

Question 2

Definition of chondroma

Answer 2

Benign cartilaginous tumours

Question 3

Classification of chondroma

Answer 3

1. Arising from diaphyseal medullary cavity
   - Enchondroma
2. Arising from surface of bone
   - Subperiosteal/juxtacortical chondroma
3. Arising from soft tissues
   - Soft tissue chondroma

Question 4

Associations with enchondromas

Answer 4

1. Ollier disease
   - Multiple enchondromas typically in a unilateral distribution
2. Maffucci syndrome
   - Multiple enchondromas with soft tissue hemangiomas
   - At risk of ovarian carcinoma & brain gliomas

Question 5

Morphology of enchondromas

Answer 5

Grossly:

1. Affected sites:
   - Only arise from endochondral bones
   - 50% of lesions are within the small bones of the hands & feet, chiefly the phalanges
   - Enchondromas are by far the most common tumour of the bones of the hand

Histologically:

1. Low-grade cartilaginous lesions composed of mature hyaline cartilage
2. Calcification, myxoid change & endochondral ossification present
3. No permeation of bone trabeculae/marrow invasion

Question 6

Clinical features of enchondromas

Answer 6

1. Xray findings:
   - Localized central lytic lesion surrounded by a sharp rim of sclerosis
   - Cortex usually not involved
2. Prognosis:
   - Solitary chondromas of long or flat bones need no treatment
   - Fractures rarely occur as they do not involve cortex
   - Recurrence unusually
   - Significant risk (25%) of malignant transformation to chondrosarcoma in Ollier disease & Maffucci syndrome

Question 7

Epidemiology & association with osteochondroma (exostosis)

Answer 7

1. Most common benign bone tumour
2. 50-75% males, mean age 10, usually aged 20 or less
3. May be sporadic or familial
   - Sporadic (85%): solitary lesions
   - Familial (15%): multiple lesions, part of hereditary exostosis syndrome (AD inheritance)

Question 8

Morphology of osteochondroma (exostosis)

Answer 8

Grossly:

1. Affected sites:
   - Only arise from endochondral bones
   - Usually occur in the metaphysis of long bones near the epiphyseal growth plate
   - Most commonly involves lower end of femur, upper end of humerus, upper end of tibia
   - Occasionally involves pelvis, scapula, ribs
2. Bony exostosis with cortex & periosteal covering of the tumour continuous with the underlying bone, attached to it by a bony stalk
3. Cut section reveals a prominent cartilaginous cap on the exostosis

Histologically:

1. Cartilage has appearance of disorganized growth plate & undergoes endochondral ossification
2. Newly-made bone forms inner portion of head & stalk

Question 9

Clinical features of osteochondroma (exostosis)

Answer 9

Complications:

- Risk of malignant transformation to chondrosarcoma (in familial multiple exostosis syndrome & adolescent exostosis)

Question 10

Epidemiology of chondrosarcoma

Answer 10

1. Most common malignant cartilage tumour
2. Usually ages 30 - 60, 75% males
   - 16% of patients may be 20 or younger (may be at higher grade & at different sites)
3. Rarely associated with pre-existing chondroma or osteochondroma

Question 11

Morphology of chondrosarcoma

Answer 11

1. Grossly:
   - Sites affected: long bones & ribs
   - Large lobulated pearly white or light blue tumour
   - Often with focal calcification
   - Myxoid change more common & suggestive of malignancy
   - Areas of haemorrhage & necrosis may be present
2. Histologically:
   - Tumour cells produce a cartilaginous matrix
   - Permeative infiltration of trabecular bone & marrow invasion
   - No osteoid formation (distinguishing factor from chondroblastic osteosarcoma)
   - ***Dedifferentiation chondrosarcoma:
   histologic variant with high grade sarcomatous transformation & low-grade cartilaginous component (highly osteosarcoma) very rare aggressive form, even more so than osteosarcomas)

Question 12

Clinical features of chondrosarcoma

Answer 12

1. Xray findings:
   - Densely calcified mass originating in the ilium adjacent to the acetabulum
   - Ill-defined margins
   - Characteristic dense speckled pattern of calcification highly suggestive of chondroid matrix
   - Perforation of the cortex
2. Treatment:
   - Tumour is radioresistant
   - Surgery mainstay of therapy
   - Little role for chemotherapy
3. Prognosis:
   - 5-year survival rate is in the range of 80%
   - Recurrence may occur 5-10 years after initial excision
   - Grading important prognostic factor:
   i. Well-differentiated: 5-yr survival = 78%
   ii. Moderately-differentiated: 5-yr survival = 53%
   iii. Poorly-differentiated: 5-yr survival = 22%
   iv. Also, distant metastases tend to occur more in higher grade tumours
   v. High grade tumour are uncommon, recur locally due to satellite nodules, metastasize early to lungs, only rarely to lymph nodes