A domestic shorthaired cat had a firm, nonpainful swelling of the left
antebrachium. Radiographs showed an expansile, multiloculated lesion
in the radius. The mass gradually enlarged over the following four and
a half months and the animal became completely lame. The histological
diagnosis was giant cell tumour of bone; this is a rare neoplasm of b
one in veterinary patients. Giant cell tumour of bone should be consid
ered in the differential diagnosis of bone lesions having an expansile
, multiloculated radiographic appearance.