Well-Differentiated, Non-Functional, Non-Ampullary Duodenal Neuroendocrine Tumors: Toward Defining Evaluation and Management

Introduction: Nonfunctional, non-ampullary duodenal neuroendocrine tumors (dNETs) are rare neoplasms, and specific treatment recommendations are less clear than for other NETs. Materials and methods: We performed a retrospective review of patients (pts) with a diagnosis of dNET, excluding hormonally functional, ampullary, and high-grade tumors. Clinical data were evaluated to identify factors that might impact clinical staging and predictors of metastases. Results: Thirty-six pts were identified. Surgical resection was performed in 28 and endoscopic resection in 8. LNs were included in specimens of 19/28 (68 %) pts who underwent surgical resection (median #LNs 5, range 1–12). Of these 19 pts, 5 (26 %) were found to be LN+. Of LN+ pts, all had tumors ≤2 cm. When compared to LN− pts, LN+ pts were more likely to have muscularis propria (MP) invasion (80 vs. 23 %, p = 0.04). Tumor size, tumor grade, lymphovascular invasion, and multifocality were similar between LN+ and LN− patients. No pt was found to have distant metastases. Heterogeneity in clinical staging modalities and small number of pts evaluated prohibited meaningful analysis of most appropriate preoperative imaging. At a median follow-up of 25 months (range 9–139), no patient developed recurrence or experienced disease-specific death. Conclusions: Non-functional, non-ampullary dNETs, particularly those with MP invasion, have a propensity to metastasize to regional LNs. However, these neoplasms appear to have a favorable prognosis. Further evaluation of preoperative imaging is required to better determine most appropriate clinical staging. A suggested workup and management strategy for prospective evaluation is proposed.