Metastatic carcinoma in the ulna of a cat secondary to a suspected pulmonary tumour

A 14-year-old male neutered Burmese cat presented for investigation of right fore limb lameness that was non-responsive to anti-inflammatory drugs and opioids. Thoracic radiography showed multiple pulmonary soft tissue nodules and a larger cavitated mass. Right elbow radiographs revealed marked peri-articular proliferation of new bone and periosteal reaction primarily affecting the ulna. Histopathological examination of an incisional biopsy of the right ulna revealed neoplastic proliferation of epithelial cells; this was confirmed as a poorly differentiated carcinoma with immunohistochemistry. Amputation of the right fore limb was performed at the owner's request. After surgery, radiographs of the limb showed progression of bone proliferation. Repeat pathological analysis confirmed a metastatic carcinoma. The cat deteriorated 3 days after surgery and was euthanased a week later as a result of severe respiratory distress. This case represents an unusual case of metastasis of a suspected primary lung tumour to the ulna in a Burmese cat.