Clear cell neuroendocrine tumor in the gallbladder diagnosed as a benign polyp preoperatively: a case report

Abstract

Background: Gallbladder neuroendocrine neoplasm is a rare disease that is divided into neuroendocrine tumors (NETs) and neuroendocrine carcinomas (NECs). Clear cell NETs of the gallbladder are extremely rare. We report the case of a patient with polypoid clear cell NET G1 of the gallbladder who underwent laparoscopic cholecystectomy.

Case presentation: A 10-mm pedunculated polyp in the gallbladder neck was detected on a follow-up abdominal ultrasound in a 60-year-old man with chronic hepatitis and hepatitis B without medication. Six months later, an abdominal ultrasound revealed that the tumor had enlarged to 12 mm in size. He was asymptomatic and had no abnormalities in other laboratory examinations, including the tumor markers, carcinoembryonic antigen and CA19-9. Abdominal ultrasound showed a 12-mm polyp in the neck of the gallbladder with perfusion and focal thickening of the gallbladder wall. A gallbladder stone was also seen in the fundus. An enhanced computed tomography scan and magnetic resonance imaging revealed a polypoid lesion and gallbladder stone located at the neck of the gallbladder and the fundus, respectively. Malignancy could not be excluded, and hence, a laparoscopic cholecystectomy was performed. Pathologically, a pedunculated polyp (14 × 11 × 15 mm) was observed in the neck of the gallbladder, and the polypoid lesion comprised nests or trabecular growths of clear NET cells in the lamina propria (ENETS: T1N0M0; AJCC: T1aN0M0). Immunohistochemical staining with synaptophysin, chromogranin A, and CD56 was confined to the tumor. The pathological diagnosis was clear cell NET G1 of the gallbladder. Although clear cell NET is often described as a distinct manifestation of von Hippel-Lindau disease (VHL), the patient had no past medical or family history of VHL. Until his one-and-a-half-year follow-up, the patient was doing well and without any signs of recurrence.

Conclusion: We report an extremely rare case of gallbladder clear cell NET G1. When NET G1 is incidentally identified in a gallbladder surgical specimen, clinical information and pathological findings should be considered as references.

Keywords: Case report; Endoscopic surgery; Gallbladder; NET; Neuroendocrine neoplasm.

Fig. 1

Representative images of the abdominal ultrasound. a A 10-mm polyp in the neck of the gallbladder was seen 6 months ago. b A 12-mm polyp in the neck of the gallbladder with perfusion and focal thickening of the gallbladder wall in the fundus. c Color Doppler imaging of the pedunculated polyp in the neck of the gallbladder

Fig. 2

Representative images from the contrast-enhanced CT scan with portal venous phase. Arrow shows a pedunculated polypoid lesion in the neck of the gallbladder (a: axial image, b: coronal image)

Fig. 3

Representative image from the T2 axial MRI. A pedunculated polypoid lesion was observed in the neck of the gallbladder

Fig. 4

Representative images with pathological findings. a A pedunculated polyp (14 × 11 × 15 mm) was observed in the neck of the gallbladder (arrow), the gallbladder wall was thickened, and Rokitansky-Aschoff sinus (RAS) could be observed clustered in the wall. b The polypoid lesion comprised solid or trabecular nests of NET cells. These tumor cells had multivacuolated clear cytoplasm (hematoxylin and eosin staining, × 40 magnification). Immunohistochemically, the tumor cells were positive for synaptophysin (c) and chromogranin A (d)