Carcinoid tumors of the urinary bladder. Immunohistochemical study of 2 cases and review of the literature.

We report the clinical, histopathologic, and immunophenotypic features of 2 carcinoid tumors of the urinary bladder and review the literature. Both tumors were located in the bladder neck, presented with hematuria, were small, and appeared to be completely excised cystoscopically. The tumors were smooth-surfaced sessile polypoid nodules covered by urothelium. Both tumors had glandular architecture. One tumor had regular bland nuclei, and the other had focal moderate nuclear pleomorphism. Neuroendocrine differentiation was readily confirmed by the immunohistochemical markers chromogranin, synaptophysin, and neural cell adhesion molecule (CD56/NCAM). In 1 of the tumors, 20% of the cells were positive for the beta subunit of human chorionic gonadotropin, and 20% were positive for thyroid transcription factor 1.