A case of neuroendocrine neoplasm of the minor duodenal papilla.

A 61-year-old woman was referred to our hospital for intraductal papillary mucinous neoplasm with no symptoms. Magnetic resonance imaging (MRI) depicted a 15 mm nodular lesion at the descending portion of duodenum. Upper gastrointestinal endoscopy showed a submucosal tumor-like mass at the minor duodenal papilla. A boring biopsy of the tumor revealed a neuroendocrine neoplasm (NEN). Various blood hormone tests were all within normal limits, and the tumor was considered to be nonfunctional. Contrast-enhanced computed tomography showed no obvious distant metastasis, and subtotal stomach-preserving pancreaticoduodenectomy (SSPPD) was performed. Histopathological examination revealed a dense cluster of spindle-shaped cells forming a sheet-like foci and areas showing glandular lumen formation, and immunohistochemistry showed synaptophysin ( + ), chromogranin ( + ). Mitotic rate was about 11 mitoses per 2 square millimeters, Ki-67 index was about 0.2%. She was pathologically diagnosed with NEN G2 at the minor duodenal papilla with regional lymph node metastasis according to the WHO2010 classification. The patient has been currently under outpatient observation with a good postoperative course. Review of the literature identified 43 cases of NENs of the minor duodenal papilla. NENs of the minor duodenal papilla have a high rate of lymph node metastasis, even if the tumor size is small.