A case report of MiNEN: concomitant primary small-cell neuroendocrine carcinoma and high-grade papillary urothelial carcinoma of the urinary badder. Composite or Collision Tumor?

Abstract

Bladder cancer is the tenth most diagnosed cancer worldwide, and urothelial carcinoma is the most common histologic type. On the contrary, small primary cell neuroendocrine carcinoma of the bladder is sporadic and accounts for less than 1% of all bladder tumors. These malignancies can be observed in mixed neuroendocrine/non-neuroendocrine neoplasms (MiNENs), which have been studied more in the gastrointestinal tract and lungs but scarcely in this organ due to their low incidence. There are concerns about the pathogenic connection between these two tumors, and the limited evidence accounts for the lack of consensus regarding prognosis and treatment for these patients; therefore, they may need a multimodal approach. Here, we describe the case of a 63-year-old woman who presented with gross hematuria, weight loss, and hypogastric discomfort for the past five months. An intravesical mass was found, and transurethral resection was performed. The Histopathology revealed a high-grade papillary urothelial carcinoma with an invasive component through muscularis propria of the bladder, so she was taken to radical cystectomy with extended pelvic lymphadenectomy. The final pathology report revealed an accompanying primary small cell neuroendocrine carcinoma intermingled with the urothelial one. She received postoperative adjuvant chemotherapy and finally died six months after surgery.