Well-differentiated neuroendocrine tumor of the urinary bladder expressing GATA 3.

Neuroendocrine neoplasms of the urinary bladder are uncommon tumors represented by small-cell neuroendocrine carcinoma and by fewer cases of large-cell neuroendocrine carcinomas and well-differentiated neuroendocrine tumors. Less than 30 examples of this latter entity have been published so far and consisted of clinically indolent lesions mainly located in the bladder neck arranged in a pseudo-glandular architecture often associated with reactive urothelial changes like cystitis cystica/glandularis. Due to their infrequency, pathologists may face difficulty to recognize this proliferation considering it as part of cystitis cystica/glandularis or misinterpreting it as nested urothelial carcinoma, paraganglioma, or secondary bladder involvement by prostatic adenocarcinoma. Herein the case of a 51-year-old female diagnosed with a well-differentiated neuroendocrine tumor of the bladder immunohistochemically expressing GATA3 is reported, pointing out either the pitfall in the differential diagnosis with cystitis cystica/glandularis, nested urothelial carcinoma, and paraganglioma or its usefulness in the differential diagnosis with prostatic adenocarcinoma.