Intramucosal-lymphatic invasion has a slight impact on lymph node metastasis in patients with early gastric cancer.

Lymphatic invasion (LI) is associated with lymph node metastasis (LNM) and a poor prognosis in patients with early gastric cancer (EGC). Although the impact of the LI volume on LNM has been described, no reports have assessed the impact of its depth on LNM. A total of 360 EGC patients with pathologically proven LI who underwent radical gastrectomy with lymphadenectomy between January 2005 and June 2018 at our institution were extracted from our database. Patients were divided into 2 groups: the mLI group, in which LI was limited to the muscularis mucosae (n = 34); and the smLI group, in which LI reached the submucosal region (n = 326). Clinicopathological features, including the LNM incidence, were compared between the groups. LNM was recognized in 3 patients (9%) in the mLI group and 101 (31%) in the smLI group (P = 0.005). In the mLI group, LNM was not recorded in any patients who met the curative criteria of ESD other than mLI. LI limited to the mucosal region does not seem to be a strong indicator for LNM. When pathological findings of an endoscopic submucosal dissection specimen show only mLI as a non-curative criterion, the probability of LNM may be very low.