[A case of neuroendocrine carcinoma in a diverticulum of the bladder].

We report a case of neuroendocrine carcinoma in a diverticulum of the bladder. A 65-year-old Japanese woman visited our hospital with the chief complaint of gross hematuria. Cystoscopy revealed a non-papillary broad-based tumor in a diverticulum of the posterior wall. She underwent transurethral resection of bladder tumor (TURBT) and subsequently total cystectomy with ileal conduit on the diagnosis of an invasive urothelial carcinoma. There was no residual tumor in the surgical specimen. Immunohistochemistry of TUR specimens showed positive synaptophysin, chromogranin A, CD56 and high ratio of positive Ki-67. Finally, it was diagnosed as a neuroendocrine carcinoma of the bladder. To our knowledge, this is the second case report of the neuroendocrine tumor or small cell carcinoma in a diverticulum of the urinary bladder in the Japanese literature.