Long-Term Complete Response of Unresectable Small-Cell Neuroendocrine Carcinoma of the Gallbladder following Chemotherapy and Radiotherapy: A Case Report.

Introduction: Small-cell neuroendocrine carcinoma of the gallbladder (SCNEC-GB) is an exceptionally rare and aggressive malignancy, representing fewer than 2% of gallbladder cancers. Most patients present with advanced, unresectable disease, and survival rarely exceeds 1 year despite therapy. Case Presentation: We describe a patient in whom SCNEC-GB was discovered incidentally during routine preoperative workup for hernia repair. Imaging revealed a bulky gallbladder mass with hepatic invasion and regional lymphadenopathy; pathology confirmed SCNEC with a Ki-67 of 100%. A multidisciplinary tumor board deemed the tumor unresectable, and systemic treatment was initiated. The patient received 6 cycles of platinum-etoposide chemotherapy, which achieved marked regression, followed by hypofractionated radiotherapy to the residual primary and nodal sites. Follow-up PET/CT demonstrated a complete radiological and metabolic response. The patient has now maintained long-term disease control for more than 18 months, with no evidence of recurrence or new metastases. Such durable remission in advanced SCNEC-GB is extraordinarily uncommon. Conclusions: This case highlights the potential of multimodal therapy to achieve long-term disease control in unresectable disease and underscores the need for collaborative efforts to define optimal strategies for this rare and lethal malignancy.