Primary small cell neuroendocrine carcinoma of the urinary bladder with coexisting high-grade urothelial carcinoma: a case report and a review of the literature.

Primary neuroendocrine carcinomas of the urinary bladder are rare. Here, we report a case of an 82-year-old man who presented with hematuria and was found to have an ulcerated lesion in the bladder. A diagnosis of small neuroendocrine cell carcinoma with coexisting minor high-grade urothelial components was rendered. In this report, the clinical, cytological, histological, and immunohistochemical features of this case are described, and a review of the literature about this neoplasm is presented. The differential diagnoses of small cell tumor in urinary bladder washing specimens are discussed.