• Toshihiko Masui, Asahi Sato, Kenzo Nakano, Yuichiro Uchida, Akitada Yogo, Takayuki Anazawa, Kazuyuki Nagai, Yoshiya Kawaguchi, Kyoichi Takaori, and Shinji Uemoto.
• Department of Surgery, Kyoto University, 54 Shogoin, Kawaracho, Sakyo, Kyoto, 606-8507, Japan. tmasui@kuhp.kyoto-u.ac.jp.
• Surg. Today. 2019 Jul 1; 49 (7): 593-600.

BackgroundWe evaluated the clinicopathological factors associated with lymph node metastasis in patients with non-functioning pancreatic neuroendocrine neoplasms (PanNENs), focusing on the risk factors and range of lymph node metastasis for tumors ≤ 2 cm in diameter.MethodsThe subjects of this study were patients with PanNENs consecutively diagnosed at our hospital between January, 2000 and June, 2018. We analyzed 69 patients who underwent R0 resection of a non-functioning sporadic PanNEN with no distant metastasis, as well as 43 patients with tumors ≤ 20 mm in radiological diameter.ResultsNineteen patients (27.5%), including 7 (16.3%) with a small PanNEN, had lymph node metastasis. A large radiological diameter, a high Ki67 index, and cyst formation correlated significantly with positive lymph node metastasis. In patients with tumors ≤ 20 mm in diameter, a high Ki67 index correlated significantly with lymph node metastasis. When we set the cut-off Ki67 index as 3.3%, 2 of 43 patients had lymph node metastasis. Tumors in the uncinate process readily metastasized to the region around the superior mesenteric artery.ConclusionsThese findings suggest that a high Ki67 index indicates a risk of lymph node metastasis for tumors ≤ 20 mm in diameter and that lymphadenectomy should be performed in the region spatially adjacent to the primary tumor.

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