According to the histologic features at the deepest level of tumor invasion (the tumor apex), we classified colorectal carcinomas as follows: well differentiated (W), moderately differentiated (M), and mucinous (Muc). By assessing its glandular configuration and cellular arrangement, the M type was further subdivided in to two different groups: moderately well differentiated (Mw) and moderately poorly differentiated (Mp) carcinomas. In our sample there were 56 W, 53 Mw, 20 Mp and 13 Muc tumors. The malignant potential of each tumor was evaluated by examining for the presence or absence of lymphatic invasion, venous invasion, lymph node metastases and liver metastases. In comparison with the other tumors, the Mp tumors proved to harbor the highest malignant potential, exhibiting a higher incidence of lymphatic invasion (95%, 19/20 of the cases), venous invasion (75%, 15/20 of the cases), lymph node metastases (80%, 16/20 of the cases), and liver metastases (40%, 8/20 of the cases). Colorectal carcinomas are composed of multiple cell populations with different biological and malignant properties, and through the histologic subclassification we could identify that Mp tumors have the highest potential to invade normal tissue and metastasize.