Benign tumours

Tumour Notes
Osteoma • benign 'overgrowth' of bone, most typically occuring on the skull
• associated with Gardner's syndrome (a variant of familial adenomatous polyposis, FAP)
Osteochondroma (exotosis) • most common benign bone tumour
• more in males, usually diagnosed in patients aged < 20 years
• cartilage-capped bony projection on the external surface of a bone
Giant cell tumour • tumour of multinucleated giant cells within a fibrous stroma
• peak incidence: 20-40 years
• occurs most frequently in the epiphyses of long bones
• X-ray shows a 'double bubble' or 'soap bubble' appearance

Malignant tumours

Tumour Notes
Osteosarcoma • most common primary malignant bone tumour
• seen mainly in children and adolescents
• occurs most frequently in the metaphyseal region of long bones prior to epiphyseal closure, with 40% occuring in the femur, 20% in the tibia, and 10% in the humerus
• x-ray shows Codman triangle (from periosteal elevation) and 'sunburst' pattern
• mutation of the Rb gene significantly increases risk of osteosarcoma (hence association with retinoblastoma)
• other predisposing factors include Paget's disease of the bone and radiotherapy
Ewing's sarcoma • small round blue cell tumour
• seen mainly in children and adolescents
• occurs most frequently in the pelvis and long bones. Tends to cause severe pain
• associated with t(11;22) translocation which results in an EWS-FLI1 gene product
• x-ray shows 'onion skin' appearance
Chondrosarcoma • malignant tumour of cartilage
• most commonly affects the axial skeleton
• more common in middle-age