Primary small-cell neuroendocrine carcinoma of the urinary bladder: A rare case and a review of the literature.

Primary small-cell neuroendocrine carcinoma (SCNEC) of the urinary bladder is a rare tumor characterized by poor differentiation and high aggressiveness. Only ~150 cases have been reported in the literature to date. We herein present a case of an 87-year-old man who presented with hematuria and was found to have an ill-defined mass in the urinary bladder on computed tomography and cystoscopic examination. On pathological examination following tumor biopsy, the mucosa of the bladder wall was found to be extensively infiltrated by neuroendocrine carcinoma, positive for CD56 and synaptophysin and negative for epithelial membrane antigen, consistent with SCNEC of the urinary bladder. The patient refused further surgical treatment and succumbed to the disease 2 months after the diagnosis. In the present study, this rare case of primary SCNEC of the urinary bladder is presented, along with a discussion on the clinical presentation, immunohistochemical and cytomorphological characteristics, management, biological behavior and prognosis of this disease.