Extraskeletal osteochondroma on a cat´s elbow.

A solitary extraskeletal osteochondroma was diagnosed in a 6-year-old, castrated male Burmese cat, positive for feline leukaemia virus (FeLV). The cat presented with a rapidly growing, solid, non-painful mass on the craniolateral aspect of the left elbow. Radiographs revealed an oval, well circumscribed 2.0 cm × 1.5 cm × 1.5 cm mineralised mass separated from the underlying bone. Surgical excisional biopsy confirmed the diagnosis. Feline extraskeletal osteochondromas are benign tumours frequently seen in FeLV-positive cats which can transform into osteosarcomas or chondrosarcomas. Radiographically, they cannot be distinguished from a parosteal or an extraskeletal osteosarcoma.