Giant cell reaction of bone.

Six cases of giant cell reaction of bone are presented. These are osteolytic lesions that affect the bones of the hand and foot. They are characterised by fibroblastic proliferation with the production of osteoid substance and bone, with abundant giant cells but no atypical cells. After describing the cases anatomically and clinically, the writers consider the differential diagnosis in bony lesions of the hand and foot containing giant cells. Giant cell reactions always heal after marginal excision. The most important differential diagnosis is with giant cell tumours and the bone lesions of primary hyperparathyroidism.