Long-Term Outcomes of Mucosal Early Gastric Cancer with Lymphatic Invasion as the Sole Non-Curative Factor After Endoscopic Submucosal Dissection

Background: The clinical significance of lymphatic invasion in mucosal early gastric cancer (EGC) treated with endoscopic submucosal dissection (ESD) remains unclear. We evaluated clinicopathologic features and long-term outcomes in patients with lymphatic invasion as the sole non-curative factor. Methods: We retrospectively reviewed 9117 patients who underwent ESD for EGC at Samsung Medical Center between 2001 and 2022. Among patients with mucosal disease and lymphatic invasion as the sole non-curative factor, long-term clinical outcomes were summarized using an outcome flowchart, and characteristics of lymph node-positive cases were analyzed in relation to curative resection criteria. Results: Among 7444 patients with mucosal EGC treated with ESD, lymphatic invasion was identified in 154 patients (2.1%). Among the 117 patients with lymphatic invasion as the sole non-curative factor, the overall rate of pathologically confirmed or clinically suspected lymph node metastasis (LNM) was 4.3% (5/117). Specifically, LNM was identified in 3.2% (3/95) of patients who underwent additional surgery, and in 9.0% (2/22, including one clinically suspected case) managed with observation alone during a median follow-up of 58.0 months. LNM was observed exclusively in lesions involving the muscularis mucosae or in lesions larger than 2 cm, whereas no LNM occurred in tumors confined to the lamina propria measuring ≤ 2 cm. Conclusions: Despite mucosal confinement, lymphatic invasion was associated with a clinically meaningful risk of LNM, whereas no LNM was observed in lesions ≤ 2 cm confined to the lamina propria. For patients with mucosal EGC in whom lymphatic invasion is the sole non-curative factor, careful, individualized decision-making is warranted.