Incidence of lymph node metastasis and the feasibility of endoscopic resection for undifferentiated-type early gastric cancer

Background: Endoscopic resection (ER) has been accepted as minimally invasive treatment in patients with early gastric cancer (EGC) who have a negligible risk of lymph node metastasis. It has already been determined which lesions in differentiated-type EGC present a negligible risk of lymph node metastasis, and ER is being performed for these lesions. In contrast, no consensus has been reached on which lesions in undifferentiated-type (UD-type) EGC present a negligible risk for lymph node metastasis, nor have indications for ER for UD-type EGC been established. Methods: We investigated 3843 patients who had undergone gastrectomy with lymph node dissection for solitary UD-type EGC at the Cancer Institute Hospital, Tokyo, and the National Cancer Center Hospital, Tokyo. Seven clinicopathological factors were assessed for their possible association with lymph node metastasis. Results: Of the 3843 patients, 2163 (56.3%) had intramucosal cancers and 1680 (43.7%) had submucosal invasive cancers. Only 105 (4.9%) intramucosal cancers compared with 399 (23.8%) submucosal invasive cancers were associated with lymph node metastases. By multivariate analysis, tumor size 21 mm or more, lymphatic-vascular capillary involvement, and submucosal penetration were independent risk factors for lymph node metastasis (P < 0.001, respectively). None of the 310 intramucosal cancers 20 mm or less in size without lymphatic- vascular capillary involvement and ulcerative findings was associated with lymph node metastases (95% confidence interval, 0-0.96%). Conclusion: UD-type intramucosal EGC 20 mm or less in size without lymphatic-vascular capillary involvement and ulcerative findings presents a negligible risk of lymph node metastasis. We propose that in this circumstance ER could be considered.