Skeletal-extraskeletal angiomatosis in a dog

An 8-year-old castrated male mixed-breed dog had an ill-defined hemorrhagic and painful lesion in the base of the claw of the second digit of the right forelimb. Radiographically, the expansile and lytic lesion affected the distal phalanx. The digit was amputated and submitted for histologic examination. Histologically, the distal phalanx was largely replaced by a mass composed of variably sized cavernous vascular spaces lined by a single layer of flattened endothelial cells. A similar mass was in the subcutis adjacent to the distal phalanx. The benign vascular proliferation involving the medulla of bone and a second tissue type in this dog is consistent with skeletal-extraskeletal angiomatosis as described in humans. To the authors' knowledge, this is the first report of skeletal-extraskeletal angiomatosis in the veterinary literature.