To establish appropriate indications for endoscopic treatment of submucosal invasive gastric carcinoma, we investigated clinicopathologic features and proliferating cell nuclear antigen (PCNA) expression at the deepest invasive portion of 192 differentiated submucosal invasive gastric carcinomas that had been surgically resected. Lymph node metastasis was demonstrated in 30 (15.6%) of 192 lesions. Histologic heterogeneity (based on differentiation at the deepest invasive portion) was demonstrated in 36 (18.8%) of the 192 lesions. In 159 lesions, excluding 33 undifferentiated lesions at the deepest invasive portion, the depth of invasion, histologic grade, lymph vessel involvement, infiltrative growth pattern (INF) and existence of an ulceration were all significantly correlated with the incidence of lymph node metastasis. The lesions with both well-differentiated adenocarcinoma (WELL) and minimal submucosal invasion (sm1) showed no lymph node metastasis. PCNA expression was estimated in 59 good stained lesions. The mean PCNA labeling index (LI) was 50.9 +/- 7.2% in lesions with lymph node metastasis and 43.7 +/- 9.3% in those without lymph node metastasis (p < 0.05). In addition, PCNA-LI also correlated significantly with the histologic grade, depth of invasion, INF and lymph vessel involvement. These results indicate that the submucosal invasive gastric carcinoma with both WELL and sm1, which shows no other risk factors, can be considered as the appropriate indication for curative endoscopic treatment. The PCNA-LI at the deepest invasive portion is useful in understanding the biology of lymph node metastasis in submucosal invasive gastric carcinoma.