Significance of the mucinous component in the histopathological classification of colon cancer

PURPOSE: Mucinous carcinoma is often independently classified as a histological type of colon cancer, but there are currently no established diagnostic criteria. The relationship between the proportions of mucinous components to the oncological outcomes was examined to determine whether mucinous carcinoma should be classified as an independent histological type. METHODS: The study group comprised 1,038 patients with colon cancer. The relationships between the survival rates and recurrence patterns with the mucinous component area ratio (MC area ratio) and clinical variables were evaluated. RESULTS: Tumors were classified into three groups: Group 1 (MC area ratio, 0 %), Group 2 (1–49 %), and Group 3 (≥50 %). Of the 1038 tumors studied, 877 (84 %) were classified as Group 1, 123 (12 %) as Group 2, and 38 (4 %) as Group 3. The tumor size was significantly larger in Group 3, and an increased MC area ratio was significantly related to a higher proportion of right-sided tumors. Among patients with stage II or III disease, stage III disease, poorly differentiated adenocarcinoma, and no adjuvant chemotherapy were poor prognostic factors. There was no relationship between the MC area ratio and the survival or recurrence pattern. CONCLUSION: Mucinous carcinoma does not need to be classified as a separate histological type from ordinary differentiated adenocarcinoma.