Primary neuroendocrine tumors of the main pancreatic duct: a rare entity.

Very few cases of primary neuroendocrine tumors of the main pancreatic duct have been reported. This paucity has hampered an accurate description of the distinctive clinical and pathological features of these tumors and the correct evaluation of the diagnostic and therapeutic problems which they may raise. We report here five additional cases in order to underline the clinical, histological, and immunohistochemical features of this tumor entity. There were three male and two female, aged 43-72 years; in all patients, but one, who presented with epigastric pain, the diagnosis was made after the incidental discovery of a dilatation of the main pancreatic duct. The preoperative diagnosis was ductal adenocarcinoma in one case, IPMN in one case and neoplastic stenosis of unknown etiology in four cases. Surgical resection was performed in all cases. The diagnosis of neuroendocrine tumor was made at histological examination. All lesions were small, ranging from 5 to 15 mm. They had a predominantly intramural growth. The growth pattern was nodular in three cases, circumferential in two; there was no intra-luminal component. All cases were well-differentiated neuroendocrine neoplasms of low histological grade (G1); four cases expressed serotonin. One case was associated with regional lymph node metastases. All cases were cured by surgery alone; no recurrence was observed at the end of the follow-up period. In conclusion, despite their rarity, primary neuroendocrine tumors of the main pancreatic duct deserve recognition and must be considered in the etiological diagnosis of ductal stenosis.