Is the Histogenesis of 6‐10 mm Early Colorectal Cancer Different from that of Larger Cancers?

: Out of a total of 466 cases of early colorectal cancer, we analyzed 139 cases with submucosal invasion (sm cancer) according to tumor size, gross appearance, depth and degree of invasion, and the presence of adenoma components. Early colorectal cancers 11 -20 mm in diameter were the most common lesion in this group, and the percentage with sm cancer increased with tumor size. More than 70% of relatively small sm cancers, 6-10 mm in diameter, had moderate or massive submucosal invasion similar to that found in large sm cancers. Only 35% of 6-10 mm cancers had an adenoma component; the majority (65%) had no adenoma component. In marked contrast, 63% of sm cancers 11 -20 mm in diameter had an adenoma component and in sm cancer the percentage of tumors composed solely of cancerous tissue without an adenoma component was low. Similar results were obtained when only protruding type sm cancers, which accounted for the majority of sm cancer cases, were included in the analysis. Therefore, we believe that the protruding type sm cancer 6-10 mm in diameter is at a stage close to advanced cancer. It is possible that many 6-10 mm sm cancers have a histogenesis different from that of large sm cancers.