[Renal carcinoid tumor presenting as bladder tamponade: a case report and review of the Japanese cases].

A 65-year-old man presented with sudden onset of gross hematuria and urinary retention. Computed tomographic scan (CT) showed a cystic multilocular enhancing lesion (9 cm in diameter) at the left renal hilum causing thinning and lateral displacement of the left renal parenchyma. Left hydronephrosis and a renal calculi were observed. We performed radical nephrectomy suspecting a cystic renal cell carcinoma. Microscopic examination and immunohistochemical studies confirmed the diagnosis of the carcinoid tumor. The tumor cells were fully positive for neuron-specific enolase and keratin, and partially positive for chromogranin-A. One of the resected lymph nodes was positive for metastasis. Additional gastrointestinal tract examinations for carcinoid tumor were negative. However, he was concurrently diagnosed with poorly differentiated prostate cancer and hormonal therapy was started. He is free of recurrent carcinoid tumor nine months postoperatively. This case is the 31st report of renal carcinoid tumors in Japan.