Pathological prognostic factors predicting lymph node metastasis in submucosal invasive (T1) colorectal carcinoma

Lymph node metastasis occurs in as many as 16% of patients with submucosal invasive colorectal carcinoma. We investigated the association between histopathological factors and lymph node metastases in 322 consecutive patients with submucosal invasive colorectal carcinoma who had undergone radical colectomy with lymph node dissection to detect patients at high risk of lymph node metastasis without measuring the depth of submucosal invasion. Lymph node metastasis was found in 46 (14.3%) of 322 patients with submucosal invasive colorectal carcinoma. Univariate analysis showed that each of the following histopathological factors had a significant influence on lymph node metastasis: invasion depth, lymphatic invasion, venous invasion, tumor differentiation, growth pattern of the intramucosal tumor component, complete disruption of the muscularis mucosa due to tumor invasion, and tumor budding at the submucosal invasive front. Multivariate analysis showed that lymphatic invasion (P<0.01), tumor differentiation (P<0.01), and tumor budding (P<0.01) were significantly associated with lymph node metastasis. All 46 cases of lymph node metastasis showed at least one of the following findings: lymphatic invasion, moderately or poorly differentiated tumor grade, tumor budding, or complete disruption of the muscularis mucosa due to tumor invasion. Patients with submucosal invasive colorectal carcinoma that show at least one of three factors--lymphatic invasion, moderately or poorly differentiated tumor grade, or tumor budding--are at high risk for lymph node metastasis. All of the patients with lymph node metastasis, who did not have any of these factors, showed a completely disrupted muscularis mucosa.