Histopathologic Criteria for Local Excision of Colorectal Cancer: Multivariate Analysis

Background: Local treatment of colorectal cancer, including endoscopic removal of colonic polyps and transanal resection of rectal tumors, has become widely accepted. However, risk factors predicting the presence of lymph node metastasis have not been fully investigated. To determine the criteria for local excision of colorectal cancer, histopathologic factors independently predicting the lymph node metastasis were investigated.Methods: We performed a retrospective histopathologic study on 335 patients who underwent resection of colorectal cancer and dissection of regional lymph nodes between 1982 and 1996. Features of node-positive tumors (n = 150) were compared with those of node-negative tumors (n = 185), with special reference to the histopathologic findings of the resected tumor. Multivariate analysis was done using the stepwise logistic regression test.Results: Node-positive tumors, when compared with node-negative tumors, were characterized by tumor larger than 6 cm (42% vs. 22%), serosal invasion (88% vs. 56%), lymphatic invasion (32% vs. 5%), venous invasion (9% vs. 2%), and histology other than well-differentiated (66% vs. 29%). Multivariate analysis showed that factors independently associated with lymph node metastasis were serosal invasion, lymphatic invasion, and histologic type. When these three risk factors were negative, lymph node metastasis was rare (5%). When one, two, or three factors were positive, the frequency of lymph node metastasis was 38%, 66%, and 85%, respectively.Conclusions: In colorectal cancer, factors independently associated with lymph node metastasis are serosal invasion, lymphatic invasion, and histologic type. When these three parameters are favorable, local treatment of colorectal cancer does not require additional lymph node dissection.