Rare case of a gallbladder neuroendocrine carcinoma

There are no neuroectodermal cells in the gallbladder mucosa. Therefore, gallbladder neuroendocrine carcinoma (NEC) is extremely rare and has a poor prognosis. We report a case of a Japanese man in his 60s with this disease. The patient visited a family doctor for epigastralgia. Blood tests showed no abnormalities, including tumor markers, such as CEA and CA19-9. Abdominal ultrasonography (US) showed a low-echoic mass, 39 × 30 mm, with clear boundaries to the liver from the fundus of the gallbladder. Contrast-enhanced computed tomography showed that the tumor was enhanced early and washed out. Diffusion-weighted MRI showed a high signal. We suspected liver invasion of gallbladder cancer and performed a cholecystectomy, S4 and S5 hepatectomy, and lymphadenectomy. The resected whitish tumor was 29 × 22 mm. The tumor cells had honeycomb growth to the liver from the gallbladder. Tumor cells were poorly differentiated, and there was no stricture of the gland duct. Immunostaining showed that the tumor cells were positive for CD56, chromogranin A and synaptophysin, and about 30% were positive for Ki-67. Our diagnosis was gallbladder NEC with liver invasion. Although most malignant gallbladder tumors are adenocarcinomas, this case indicates that gallbladder NEC should be considered as a differential diagnosis of gallbladder tumor.