Chondro-osteoblastic metaplasia in canine benign cutaneous lipomas

Lipomas are common benign adipose tissue tumours in dogs. Variants of lipomas are characterized by an additional component (e.g. capillaries in angiolipomas or fibrous connective tissue in fibrolipomas). In human medicine, the presence of cartilage or bone within a lipoma is a rare event. Mechanical stress, tropic disturbances, contact with periosteum and other unknown factors may contribute to this transformation. The present report describes the clinical, gross and microscopical findings of four cases of chondrolipoma and two cases of osteolipoma in the canine skin. The possible histogenesis for these tumours in the dog is discussed.