Lymphadenectomy during Small Bowel Neuroendocrine Tumor Surgery: The Concept of Skip Metastases.

BACKGROUND: More than half of small bowel neuroendocrine tumors (SB-NETs) are metastatic at diagnosis, but complete resection of the primary tumor and lymph node (LN) is recommended by most authors. Our aim was to describe the pattern of involved LN after an extensive LN resection.

MATERIALS AND METHODS: Between July 2013 and December 2015, all consecutive patients who underwent resection of at least one SB-NET in our European Neuroendocrine Tumor Society Center of Excellence were prospectively included, while patients with duodenal SB-NETs were excluded. The resection and pathological analysis of LNs were standardized using three groups (group 1, along the small intestine; group 2, along the mesenteric vessel; and group 3, retropancreatic and mesenteric vessel origin).

RESULTS: Twenty-eight patients with SB-NET resection were prospectively enrolled in the study, with seven patients being excluded from the analysis because it was impossible to divide the operative piece into nodal groups due to retractile mesenteritis. Among the remaining 21 patients, 20 (95 %) had LNs involved; 8 (38 %) in group 1, 13 (62 %) in group 2, and 12 (57 %) in group 3. Skip metastases were found in 14 patients (67 %): 4 (19 %) with an invasion pattern of group 3+ without group 2+, and 12 (57 %) with an invasion pattern of group 2+ or group 3+ without group 1+.

CONCLUSION: As a result of skip metastases, systematic, extensive LN resection in retropancreatic portion may be required to prevent unresectable locoregional recurrence.