A case report of carcinoid tumor presenting as choledocholithiasis: An uncommon culprit in a common crime

Primary gallbladder neuroendocrine tumors (NETs) are exceedingly rare, comprising <1% of all NETs and approximately 2.3% of gallbladder malignancies. Due to their rarity and nonspecific presentation, they are frequently diagnosed incidentally following cholecystectomy for presumed benign biliary disease. A 61-year-old female presented with right upper quadrant pain, nausea, vomiting, and intermittent fevers. Laboratory studies demonstrated leukocytosis, elevated alkaline phosphatase, and mildly elevated direct bilirubin. Imaging revealed acute calculous cholecystitis with choledocholithiasis. She underwent ERCP with removal of four pigment stones, followed by robotic cholecystectomy for persistent symptoms and gallbladder inflammation. Intraoperative findings included a friable gallbladder with dense adhesions and multiple gallstones. Final pathology revealed a well-differentiated, low-grade neuroendocrine tumor with positive chromogranin and synaptophysin staining and a low Ki-67 index. Surgical margins were negative. The patient recovered uneventfully and was discharged on postoperative day two. Gallbladder NETs often mimic benign biliary disease, contributing to a preoperative misdiagnosis rate exceeding 90%. Chronic inflammation and cholelithiasis may contribute to tumor development. Due to limited case numbers, management strategies are extrapolated from gallbladder adenocarcinoma guidelines, with surgical resection considered adequate for localized, low-grade disease. Gallbladder neuroendocrine tumors are rare and frequently discovered incidentally after surgery for presumed benign pathology. This case highlights the importance of histopathologic evaluation and contributes to the limited literature guiding recognition and management of this uncommon malignancy.