Neuroendocrine tumor of the minor duodenal papilla with lymph node metastasis: a case report and literature review.

Whether pancreatoduodenectomy or papillary resection should be performed to achieve curative treatment for neuroendocrine tumors of the minor duodenal papilla with a diameter of ≤2 cm is controversial. We report a 35-year-old male patient with a rare case of a neuroendocrine tumor of the minor duodenal papilla. The patient was referred to our hospital from a different clinic for dilatation of his minor duodenal papilla. Duodenoscopy revealed a smooth mass of 2 cm in diameter in the minor papilla, and the biopsy specimen was diagnosed as neuroendocrine tumor G1. The patient underwent subtotal stomach-preserving pancreatoduodenectomy. Histological evaluation showed a single nodule of 15 mm in diameter in the mucosa with metastasis to the regional lymph node. The tumor cells exhibited immunoactivity against synaptophysin and chromogranin A. The molecular immunology Borstel-1 index was less than 1%, and the grade was neuroendocrine tumor G1. We reviewed the characteristics of 24 cases of patients who underwent PD for NETs of the minor duodenal papilla in English literature. In 22 of these cases, the tumor depth was described. Lymph node metastasis was observed in none of the three cases (0%) in which the tumor was limited to the intra-sphincter; however, it was noted in three (30%) of the 10 cases in which the tumor had invaded the duodenal submucosa and in eight (89%) of the nine cases in which the tumor had invaded the muscularis propria, pancreas, peripancreatic/periduodenal tissues, or duodenal serosa. Making a definitive diagnosis preoperatively or intraoperatively whether the tumor invades beyond the sphincter or not and whether regional lymph node metastasis is present may not be possible. Therefore, we believe that pancreatoduodenectomy with lymphadenectomy is preferable for curative treatment of neuroendocrine tumors of the minor duodenal papilla.