Abstract
Primary gallbladder neuroendocrine tumor (GB-NET) is extremely rare. Therefore, tumor behavior and adequate treatment in GB-NETs are still unclear. A 74-year-old man without any specific complaints was referred to our hospital cause of gallbladder tumor. Abdominal ultrasonography examination revealed a 22-mm non-pedunculated tumor in the gallbladder body. Contrast-enhanced computed tomography showed a polyp that was enhanced in the arterial phase. The patient underwent gallbladder bed resection and radical lymphadenectomy with a diagnosis of gallbladder carcinoma. Macroscopically, the resected specimen showed a nodular expanding tumor measuring 32×15 mm in the gallbladder body. From the pathological findings, a grade 3 GB-NET was diagnosed. Only cystic lymph node metastasis was observed. The patient was discharged uneventfully, but bone and lymph node metastasis were detected eight months after surgery. We conclude that grade 3 GB-NET shows occasionally malignant biological behavior although NET G3 is distinguished from neuroendocrine carcinoma in the current WHO 2019 classification of NET.