Benign tumours: relatively rare and the most common is the osteochondroma, a bony polyp with a cap of hyaline cartilage seen usually in long bones. Enchondromas are cartilaginous tumours occurring in the medullary cavity of long bones. Osteoid osteoma is a painful lesion occurring in the cortex of a long bone, with a central lytic nidus and a margin of sclerotic bone. A giant cell tumour of bone is seen in people aged 20 to 40 years of age and characteristically represents a lytic lesion occurring in the epiphysis of long bones. Other benign tumours include osteoblastoma, chondroblastoma and chondromyxoid fibroma but these are very rare.
Tumour-like conditions: includes cysts, reparative granulomas, fibrous dysplasia, benign fibrous histiocytoma and eosinophilic granuloma.
Primary malignant tumour: these are also rare and most commonly seen in young people and children. Osteosarcoma is a high-grade sarcoma producing malignant osteoid, typically seen in the metaphysis of long bones and people aged 10 to 25 years old. It is very rare in older people but can be associated with previous radiation exposure and Paget's disease. It is treated by a combination of chemotherapy and surgery. Ewing's sarcoma is a poorly differentiated, small, round, blue cell tumour seen in the long bones of children and young adults. It is treated with a combination of chemotherapy, radiotherapy and surgery. Chondrosarcomas are usually low-grade sarcomas occurring in long bones and flat bones in middle-aged and older people. They have a tendency for recurrence rather than metastasis. They do not respond to chemotherapy and treatment is surgical removal. The dedifferentiated chondrosarcoma is a high-grade tumour, typically large in size occurring in the pelvis and proximal femur of older people. These tumours metas-tasise early and have an extremely bad prognosis.
Multiple myeloma: this is really a haematological tumour but sometimes classified as a bone tumour. It is a tumour arising from the plasma cells and occurs in multiple skeletal sites. It is treated with chemotherapy.
Metastatic carcinoma: this is by far the most common malignant tumour in bone and presents as bone pain or pathological fracture. The most common primary sites are lung, kidney, breast, prostate and thyroid. Most metastatic tumours produce lytic lesions but prostatic secondaries are often sclerotic. The usual skeletal sites are proximal long bones, rib, pelvis and vertebrae. Metastatic disease is distinctly uncommon in the skeleton distal to the elbow or knee.
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