Primary gallbladder neuroendocrine neoplasm: A case report of grade 1 well-differentiated neuroendocrine tumor.

Introduction: Neuroendocrine neoplasm (NENs) make up approximately 2-3 % of gallbladder malignancies, while only 0.5 % of all NENs develop in the gallbladder. Most Gallbladder neuroendocrine neoplasms (GB-NENs) are discovered incidentally during pathological examinations post-cholecystectomy.

Case presentation: 70-year-old male presents with an incidentally discovered 2.2 cm enhancing intraluminal soft tissue mass on abdominal CT scan. The mass demonstrates restricted diffusion on MR imaging, concerning for gallbladder malignancy. Radical cholecystectomy, confirms primary gallbladder neuroendocrine tumor (GB-NET). No adjuvant therapy was recommended at multidisciplinary cancer conference review. The patient is currently disease free at 18 months follow up.

Discussion: The management of GB-NEN remains challenging, due to the lack of specific clinical manifestations and typical imaging features preoperatively. GB-NENs are usually asymptomatic, and the paucity of reported imaging characteristics makes prospective diagnosis of GB-NENs challenging. GB-NEN tend to be larger in size, demonstrating well defined, intact mucosa, with a thick rim of hyperintensity on diffusion weighted images (DWI). Distinguishing between gallbladder neuroendocrine carcinoma (GB-NEC) and gallbladder neuroendocrine tumor (GB-NET) on pathologic evaluation is essential in developing a treatment plan. GB-NETs have superior survival compared to GB-NECs. GB-NETs can be managed utilizing a cholecystectomy with portal lymphadenectomy +/- segment 4b/5 liver resection.

Conclusion: GB-NETs may achieve curative resection, if identified at an early disease stage.