Sarcomatoid renal cell carcinoma with osteogenic differentiation and paraneoplastic hepatopathy in a dog, possibly related to human Stauffer's syndrome.

Sarcomatoid renal cell carcinoma is an uncommon tumour in human beings, and osteogenic differentiation is a rare feature. This report describes such a case in a male dog aged 8 years. The tumour, which showed extensive osseous metaplasia and a few necrotic areas, protruded into the renal pelvis, disrupting the renal capsule. Light microscopical and immunohistochemical examination revealed the epithelial nature of the tumour. Abnormal liver biochemistry, mild hepatocyte degeneration and the absence of histological evidence of metastasis suggested a paraneoplastic hepatopathy.