Abstract
We report a rare case of neuroendocrine tumor (NET G1) in the gallbladder. A 47-year-old man was admitted to our hospital with a gallbladder polyp detected by routine ultrasonography. Ultrasonography showed an 11-mm-diameter sessile polypoid tumor with an irregular surface in the gallbladder neck, which was enhanced on CT. MRCP showed a defect in the gallbladder neck, but no bile duct abnormality. He underwent laparoscopic cholecystectomy for suspected adenoma or early-stage gallbladder cancer. Histopathological examination of the tumor in the resected gallbladder showed proliferation of monotonous tumor cells with small round nuclei and pale to lightly eosinophilic abundant cytoplasm in variable-sized islands or nests in the stroma of the gallbladder epithelium indicating papillary growth. The tumor nests partly infiltrated the subserosa. No mitotic figures were observed. Immunohistochemically, the tumor cells were positive for chromogranin A and synaptophysin, and the Ki-67 index was 1%. Based on these findings, he was diagnosed with NET G1 of the gallbladder.
