AIM:To study how lymph node metastasis(LNM) risk is stratified in undifferentiated-type early gastric cancer(undiff-EGC) dependent on combinations of risk factors.METHODS:Five hundred and sixty-seven cases with undiff-EGC undergoing gastrectomy with lymphadenectomy were examined retrospectively.Using clinicopathological factors of patient age,location,size,an endoscopic macroscopic tumor form,ulceration,depth,histology,lymphatic involvement(LI) and venous involvement(VI),LNM risk was examined and stratified by conventional statistical analysis and datamining analysis.RESULTS:LNM was positive in 44 of 567 cases(7.8%).Univariate analysis revealed > 2 cm,protrusion,submucosal(sm),mixed type,LI and VI as significant prognostic factors and > 2 cm and LI-positive were independent factors by multivariate analysis.In preoperatively evaluable factors excluding LVI,sm and > 2 cm were independent factors.According to the depth and size,cases were categorized into the low-risk group [m and ≤ 2 cm,0%(LNM incidence)],the moderaterisk group(m and > 2 cm,5.6%; and sm and ≤ 2 cm,6.0%),and the high-risk group(sm and > 2 cm,19.3%).On the other hand,LNM occurred in 1.4% in all LI-negative cases,greatly lower than 28.2% in all LI-positive cases,and LNM incidence was low in LInegative cases even in the moderate- and high-risk groups.CONCLUSION:LNM-related factors in undiff-EGC were depth and size preoperatively while those were LI and size postoperatively.Among these factors,LI was the most significantly correlated factor. AIM: To study how lymph node metastasis (LNM) risk stratified in undifferentiated-type early gastric cancer (undiff-EGC) dependent on combinations of risk factors. METHODS: Five hundred and sixty-seven cases with undiff-EGC undergoing gastrectomy with lymphadenectomy Useful clinicopathological factors of patient age, location, size, an endoscopic macroscopic tumor form, ulceration, depth, histology, lymphatic involvement (LI) and venous involvement (VI), LNM risk was examined and stratified by conventional statistical analysis and Univariate analysis revealed> 2 cm, protrusion, submucosal (sm), mixed type, LI and VI as significant prognostic factors and> 2 cm and LI-positive were independent factors by multivariate analysis. In preoperatively evaluable factors excluding LVI, sm and> 2 cm were independent factors. According to the depth and size, cases were categorized into the low-risk group [m and ≤ 2 c the moderator group (m and> 2 cm, 5.6%; and sm and ≤ 2 cm, 6.0%) and the high-risk group (sm and> 2 cm, 19.3% .On the other hand, LNM occurred in 1.4% in all LI-negative cases, greatly lower than 28.2% in all LI-positive cases, and LNM incidence was low in LInegative cases even in the moderate- and high-risk groups .CONCLUSION : LNM-related factors in undiff-EGC were depth and size preoperatively while those were LI and size postoperatively. Among these factors, LI was the most significantly correlated factor.