Mucosal Small Cell Neuroendocrine Carcinoma of the Gallbladder With Extraregional Lymph Node Metastasis: A Case Report.

Gallbladder small cell neuroendocrine carcinoma (SCNEC) is a rare and highly aggressive malignancy, and an optimal treatment strategy has not been established. We report a case of mucosal gallbladder SCNEC with extraregional lymph node metastasis that responded well to chemotherapy. A 69-year-old woman presented with severe epigastric pain and inflammatory findings. Ultrasonography, endoscopic ultrasonography, and computed tomography revealed a 40 mm gallbladder mass and enlarged lymph nodes in the hepatoduodenal ligament. Because inflammation and pain could not be controlled by conservative treatment and endoscopic gallbladder drainage was unsuccessful, emergency laparoscopic cholecystectomy was performed. Histopathological examination revealed SCNEC with a Ki-67 index of 80%. Although continuous tumor invasion was limited to the mucosal layer and the tumor was classified as T1a, lymphatic invasion was present. Postoperative positron emission tomography and octreotide scintigraphy revealed metastases in the hepatoduodenal ligament and extraregional perisplenic artery lymph nodes. Further surgical resection was not performed, and chemotherapy with cisplatin and irinotecan was initiated. After six cycles, the hepatoduodenal ligament lymph node decreased from 31 mm to 13 mm, and the perisplenic artery lymph node disappeared, resulting in a partial response. No disease progression was observed during the 12-month postoperative follow-up period. This case suggests that gallbladder SCNEC may have metastatic potential even when the primary tumor is limited to the mucosal layer. Careful systemic staging is important, and platinum-based chemotherapy may be effective for metastatic disease.