[Non-functional duodenal neuroendocrine neoplasia in the proximal duodenum--case reports and proposal for a "high-risk-/low-risk-concept" in the decision for local endoscopic therapy].

Early duodenal neuroendocrine neoplasms (dNENs) are being increasingly diagnosed. Non-functional dNENs in the bulb expressing gastrin are by far the most frequent entity. In the period from 2004 to 2012, 17 cases of 16 patients with NET in the duodenal bulb were evaluated. dNENs of the ampulla of Vater and functional dNEN/gastrinoma were not included due to possibly different malignant potentials. The average age of the patients was 65.7 years, the mean tumour size was 10.2  mm, the maximum proliferation index Ki 67 was 5 % (NET G2). In most cases the maximum depth of invasion was down to the submucosa. In cases of dNEN without risk factors (size up to 10 mm, G1 situation, no invasion of the muscularis propria, no angioinvasion) in 10 out of 11 cases (90.9 %), endoscopic therapy was sufficient. In cases of existing risk factors, sole endoscopic treatment was only possible in 1 out of 5 cases (20 %). In the absence of risk factors in the current follow-up period (mean: 36.7 months) no lymph node metastases were detected. In the presence of risk factors or indications for surgery we found an increase in the rate of lymph node metastases. Our own data indicate that in case of a G2 situation, a tumour size >10  mm or infiltration of the muscularis propria the need for surgical treatment increases significantly for early non-functional dNENs in the duodenal bulb. A high-risk-/low-risk-concept for the endoscopic therapy for early non-functional dNEN has been established.