The diagnosis of bilateral primary renal paragangliomas in a cat

A 9-year-old sterilised female domestic short-hair cat was referred with a history of vomiting and anorexia of 3 months' duration. Biochemistry, full-blood counts, thoracic radiographs, feline pancreatic-specific lipase, abdominal ultrasonography and feline immunodeficiency virus/feline leukaemia virus (FIV/FeLV) SNAP tests had been performed. Mild hypochloraemia and moderate hypokalaemia were evident on initial presentation. Abdominal ultrasonography initially revealed unilateral renal nodules on the left side. These were subjected to fine-needle aspiration and cytological evaluation. A neuroendocrine tumour was suspected, and biopsies via midline coeliotomy were taken to confirm the diagnosis. Initial histopathology diagnosed primary renal carcinomas or neuroendocrine neoplasia; however, the definitive diagnosis became renal paragangliomas after immunohistochemistry and transmission electron microscopy were performed. The cat was regularly monitored with serum biochemistry parameters, blood pressure determinations, thoracic radiographs and subsequent abdominal ultrasonography. Biochemistry, radiography and blood pressures remained normal over a 24-week follow-up period, while subsequent ultrasonography revealed tumour progression in both number and size in both kidneys. Primary neuroendocrine tumours of the kidney are frequently incorrectly diagnosed as other renal tumours such as renal cell carcinoma, mesonephric tumours or undifferentiated carcinomas. This case report highlights the importance of additional testing, including immunohistochemistry and transmission electron microscopy, to obtain a definitive diagnosis of paragangliomas.