[A Preoperatively Diagnosed and Resected Case of Neuroendocrine Tumor of the Ampulla of Vater].

A 50-year-old male was diagnosed with a submucosal tumor of the ampulla of Vater, as determined by esophagogastroduodenoscopy 9 months before surgery. EUS revealed that the submucosal tumor had invaded the sphincter of Oddi surrounding the ampulla of Vater, and tumor biopsy revealed neuroendocrine tumor(NET)Grade 1(G1). As contrast-enhanced computed tomography showed no obvious lymph node or distant metastasis, a subtotal stomach-preserving pancreaticoduodenectomy with lymph node dissection was performed. Microscopic examination of the resected 1.8×1.5 cm tumor showed that eosinophilic and oval atypical cells with tubular or alveolar structures, which tested positive for synaptophysin, chromogranin A, and CD56 on immunohistochemistry, invaded the sphincter of Oddi of Vater papilla. The Ki-67 labeling index was <1%, and lymph node metastases were detected, with a diagnosis of NET G1, pT2N1M0. Because NET of the ampulla of Vater tends to spread to the lymph nodes, radical resection with lymph node dissection is recommended. However, the indications for endoscopic or papillary local resection of small NETs(<2 cm)of the ampulla of Vater are controversial. We report a rare preoperative diagnosis and resected case of NET of the ampulla of Vater, along with the findings of previous studies.