[Bladder Metastasis of Renal Cell Carcinoma 7 Years after Ex Vivo Partial Nephrectomy and Auto-Transplantation : A Case Report].

Metastasis of renal cell carcinoma (RCC) to urinary bladder is extremely rare. We report a case of metastasis arising from RCC to the urinary bladder 7 years after treatment of bilateral RCC. A 74-year-old man was diagnosed with bilateral multiple renal tumors (T1aN0M1, PUL, OSS) with two lesions in the right kidney and a solitary lesion of the left kidney in 2008. He underwent laparoscopic radical nephrectomy for the right side in September 2008. The next month, ex vivo partial nephrectomy and auto-transplantation was performed for the left kidney because the tumor was located very close to the collecting system. Metastatectomies for the lung and bone followed and the histopathological findings of all lesions were clear cell carcinoma. The following years went well without any recurrence. Seven years after the surgery, the patient complained of asymptomatic gross hematuria and cystoscopy revealed a solitary non-papillary tumor of the bladder. Transurethral resection of the tumor was performed in June 2015 and the histopathological diagnosis of the resected specimens was clear cell carcinoma. Because the additional immunohistochemical examinations were positive for CD10 and negative for CK7, we diagnosed the bladder tumor as metastasis arising from RCC. Direct dissemination of the tumor cells into the urinary tract during partial nephrectomy followed by implantation to the bladder mucosa is a probable mechanism of metastasis in this case.