Uncommon but aggressive: A case series on urinary bladder neuroendocrine carcinomas

Neuroendocrine carcinomas (NECs) of the urinary bladder are rare, accounting for less than 1% of all bladder malignancies, and are characterized by aggressive behavior and poor prognosis. These tumors can occur as small or large cell subtypes and often mimic high-grade urothelial carcinoma, posing diagnostic challenges. We present five cases of bladder NECs diagnosed at our center, all presenting with hematuria and other lower urinary tract symptoms. Tumor sizes ranged from 4.8 to 7.5 cm, with all demonstrating deep muscle invasion and high proliferative index. Immunohistochemistry confirmed neuroendocrine differentiation. Four patients received platinum-based chemotherapy, and one underwent radical cystectomy. Two patients with advanced-stage disease succumbed early despite therapy. This series highlights the importance of early recognition, accurate histopathological diagnosis, and timely multimodal management. Given their rarity and diagnostic overlap with other high-grade bladder tumors, clinical awareness is crucial.