Neuroendocrine Tumor: A Rare, Aggressive Tumor of the Gallbladder

We report a case of rare and aggressive gallbladder neuroendocrine carcinoma (GB-NEC), diagnosed with the help of endoscopic ultrasound (EUS). A 65-year-old asymptomatic male, with a past medical history of hypertension, underwent abdominal ultrasound for the screening of an abdominal aortic aneurysm. He was found to have a mixed echogenicity area near the stomach, an incidental finding on abdominal ultrasound. The patient had an upper gastrointestinal (GI) endoscopy exam, which revealed an antral mass that was biopsied. The tissue specimen showed an epithelioid mesenchymal tumor of unclassified type and, eventually, the patient underwent partial gastrectomy. Surgical pathology reported a low-grade sub-serosal gastrointestinal stromal tumor (GIST) of the resected tissue specimen. He was later discharged and advised to follow up with abdominal computed tomography (CT) every year. Two years later, his abdominal CT revealed a new 3.7 cm x 2.0 cm mass in the posterior gallbladder fundus. Subsequently, the patient underwent laparoscopic cholecystectomy and the excisional biopsy reported a T3NXM1 neuroendocrine small cell carcinoma. Then, he received six cycles of systemic chemotherapy with carboplatin and etoposide, showing excellent response initially. However, a repeat CT abdomen/pelvis with contrast, on his eighth-month follow-up, demonstrated the interval development of an infiltrative mass in the pancreatic head. The gastroenterology team was then consulted, who performed sphincterotomy with temporary stent placement and celiac plexus neurolysis. Also, a transduodenal fine-needle aspiration (FNA) of the pancreatic mass was performed, which revealed metastatic small cell carcinoma. Based on these findings, the patient received an additional three cycles of carboplatin/etoposide chemotherapy, along with one cycle of immunotherapy. However, the patient had a poor response to chemotherapy, and he eventually chose hospice care.