Endoscopic mucosal resection (EMR) is currently not accepted as an alternative treatment to surgery in early gastric cancer (EGC) of the undifferentiated histologic type. The present retrospective analysis examined the correlation of various histologic factors with the presence of lymph node metastasis (LNM). A retrospective analysis on 234 patients with poorly differentiated EGC who underwent radical gastrectomy with D2 lymph node dissection was undertaken. Several clinicopathologic factors were investigated to identify predictive factors for LNM: age, sex, type of operation, tumor location, tumor size, gross type, ulceration, lymphatic invasion, and depth of invasion. Of the 234 lesions with poorly differentiated EGC, half (n = 116) already showed submucosal invasion in the resection specimen; 25.9 % of those (30/116) were limited to the upper third (SM1). Of the lesions confined to the mucosa, LNM was found in 3.4 % (4/118). With minor submucosal infiltration (SM1), the LNM rate was lower (0/30) in our patient population. Only with SM2/3 infiltration did the LNM rate sharply rise to around 30 %. The cut-off for submucosal infiltration depth was 500 microm (0/32 LNM), above which LNM rates were substantial (31.2 %; 24/77). There was limited correlation between the SM1-3 classification and actual measurement of submucosal infiltration depth. In a multivariate analysis, tumor size ( P = 0.033), depth of invasion ( P = 0.004), and lymphatic invasion ( P < 0.001) were associated with LNM. Poorly differentiated EGC confined to the mucosa or with minimal submucosal infiltration (<or= 500 microm) could be considered for curative EMR due to the low risk of LNM. Given the limited case number of subgroups, these findings should be confirmed by more data from other centers, which should also focus on local recurrence after EMR in poorly differentiated EGC.