A rare case of Primary Small Cell Neuroendocrine Carcinoma of the Renal Pelvis: Case Report and Literature Review

Background Neuroendocrine neoplasms (NENs) constitute a rare and highly aggressive category of malignant tumors that arise from cells within human tissues and exhibit diverse neural and endocrine functionalities. These tumors predominantly occur in the gastrointestinal tract, pancreas, lungs, and various other organs. However, primary small cell neuroendocrine carcinoma (SCNEC) of the urinary tract is relatively uncommon in clinical settings. Case Presentation: We present a case of primary small cell neuroendocrine carcinoma (SCNEC) of the ureter. The patient was admitted for the management of hematuria and abdominal pain, with a significant past medical history of multiple kidney stone surgeries. Following a comprehensive medical evaluation and a diagnostic ureteral biopsy, the patient was definitively diagnosed with SCNEC. The patient subsequently underwent surgical intervention and was administered a comprehensive treatment regimen consisting of chemotherapy augmented with tislelizumab. Regrettably, the patient died from disease progression one month postfollow-up. Conclusions Small cell neuroendocrine carcinoma (SCNEC) of the urinary system represents an exceptionally rare and aggressive malignant tumor, but its precise etiology and pathogenesis remain elusive. On the basis of the current body of research, we hypothesize that the emergence of these tumors may be linked to repeated cellular injury and regenerative processes. Through meticulous analysis of the presented case, we emphasis that, in clinical practice, suspected SCNEC patients should promptly undergo pathological biopsy to confirm the diagnosis, thereby ensuring timely and accurate patient management. For patients with sufficient physiological reserve to undergo surgery, we advocate for an aggressive surgical approach aimed at curative resection or debulking, in conjunction with a multidisciplinary treatment regimen encompassing chemotherapy and immunotherapy, with the aim of prolonging patient survival.