Osteosarcomas, [s8]uncommon

About half of all primary bone sarcomas are osteosarcomas; they occur either in teenagers, or as a complication of Paget's disease in men over 60 (rare). They are aggressive tumours of osteoblasts, and either spread by local infiltration, or in the bloodstream to the lungs, often quite early.

An osteosarcoma usually presents as a painful swelling or pathological fracture of the metaphysis of the lower femur (40%), upper tibia (20%), upper humerus (10%), or pelvis (10%).

OSTEOSARCOMA X-RAYS. (1) Typically, there is an osteolytic lesion of the metaphysis, which expands the periosteum, and produces a triangle (Codman's triangle), of increased density where the tumour meets the normal shaft. You may see lines of ''sun ray' bone spicules. (2) A few are small lesions with dense osteosclerosis round a lytic lesion with intramedullary ''fluff'.

SPECIAL TESTS The alkaline phosphatase is usually raised. Confirm the diagnosis by biopsy.

THE DIFFERENTIAL DIAGNOSIS. (1) Very important, early acute osteomyelitis; this causes much pain and shows no bone changes (7.2). (2) The subacute form produces a periosteal reaction. (3) Chronic osteomyelitis causes dense sclerosis, often with sinuses, and usually involves an extensive area of the shaft.

Other differential diagnoses include ordinary fractures (especially if they present late), stress fractures (fatigue fractures, 81.8), simple bone cysts, exostoses, secondary tumours, and other primary bone tumours.

CAUTION ! Osteosarcomas may cause fever.

THE PROGNOSIS is grim, and there are few long-term survivors. The tumour extends considerably beyond the area of the bone which is involved clinically, or radiologically. 75% of patients have lung secondaries when they present, or within 6 months, even if an amputation has been done.

MANAGEMENT in the past depended on amputation through the bone or joint immediately above the tumour, or disarticulation through the hip. Although the tumour is rather radioresistant radiotherapy is usually given, and is followed in 6 months by amputation, if there are no secondaries (this routine avoids amputation in those who would develop secondaries quite soon).

Some regimes increase the disease-free interval after surgery, but none increase the survival time. Here is one: it is of limited value, so it should not have high priority: Vincristine 1.4 mg/m['2] on Day 1. Actinomycin D 2 mg/m['2] on Days 1 and 3. Cyclophosphamide 1 to 1.5 g/m['2] on Day 1.

If there are no metastases, amputate if this is practicable.

If there are metastases, chemotherapy will not cure, but may be helpful for palliation or pain.