Solitary distal limb Mast Cell Tumor in a three year old Arabian mare

A 3 year old Arabian mare was presented to the Veterinary Teaching Hospital, Koret School of Veterinary Medicine, with a mass on the dorsal aspect of the left metatarsus, immediately distal to the tarsus. Ultrasonographic evaluation showed a soft tissue mass with some dotted hyperechogenicity and no involvement of the extensor tendons. Radiographs demonstrated a mass of soft tissue opacity with areas of mineralization and no bone involvement. The mass was injected with triamcinolone (18 mg) but continued to grow. It was removed surgically under general anesthesia and submitted for histopathologic examination. Microscopic evaluation demonstrated a mast cell tumor which had been excised with clean margins. Four years later, there was no recurrence and the mare was used, as intended, for reproductive purposes.