Neuroendocrine tumors in the urinary bladder: a literature review

Neuroendocrine tumors (NETs) can be found in most organs, as well as in the urinary bladder. Some of the clinical and pathologic features of these tumors may be characteristic of the organ of origin, but most of the properties are shared by neuroendocrine neoplasms regardless of their anatomic site. In the bladder, NETs comprise less than 1% of all bladder tumors and can be found in a pure form or intermixed with urothelial carcinoma and its variants. Bladder NETs are classified into 2 subtypes: carcinoid tumor and neuroendocrine carcinoma, which is further subdivided into small cell and large cell neuroendocrine carcinoma. Characteristics of bladder NETs and its differential diagnosis are discussed herein.