Renal cell carcinoma in a cat with polycystic kidney disease undergoing renal transplantation.

case summaryA 10-year-old spayed female American Shorthair cat underwent renal transplantation due to worsening chronic kidney disease secondary to polycystic kidney disease. During transplantation, the right kidney grossly appeared to be more diseased than the left and was firmly adhered to the surrounding tissues. An intraoperative fine-needle aspirate of the right native kidney revealed inflammatory cells but no evidence of neoplasia. To create space for the allograft, a right nephrectomy was performed. Following nephrectomy, the right native kidney was submitted for biopsy. Biopsy results revealed a renal cell carcinoma. Although the cat initially recovered well from surgery, delayed graft function was a concern in the early postoperative period. Significant azotemia persisted and the cat began to have diarrhea. Erythematous skin lesions developed in the perineal and inguinal regions, which were suspected to be secondary to thromboembolic disease based on histopathology. The cat's clinical status continued to decline with development of signs of sepsis, followed by marked obtundation with uncontrollable seizures. Given the postoperative diagnosis of renal cell carcinoma and the cat's progressively declining clinical status, humane euthanasia was elected. RELEVANCE AND NOVEL INFORMATION: This case is the first to document renal cell carcinoma in a cat with polycystic kidney disease. An association of the two diseases has been reported in the human literature, but such a link has yet to be described in veterinary medicine. Given the association reported in the human literature, a plausible relationship between polycystic kidney disease and renal cell carcinoma in cats merits further investigation.