Clinicopathologic Study on Colorectal Cancer 20mm or Less in Size Invading Muscularis Propria

Abstract

This study was carried out to clarify the clinicopathologic and biological features of small advanced colorectal cancers (CRC). A total of 91 cases of CRC invaded muscularis propria were analyzed, and 11 cases 20 mm or less in size (cancer≤20 mm) were compared with the remaining 80 (cancer>20 mm). The depth of invasion of cancer≤20 mm was shallower than that of cancer>20 mm and patients with cancer≤20 mm were younger than those with cancer>20 mm. As for cancer differentiation, the proportion of moderately-differentiated cancer as compared to well-differentiated cancer was higher in cancer≤20 mm. Although the DNA ploidy pattern did not differ between the groups, the mean DNA index in cancer≤20 mm was significantly lower. As for the growth form according to the classification of Shimoda, all cancers were divided into two groups, polypoid growth type (PG) and non-polypoid growth type (NPG). The mean size of NPG was significantly smaller than that of PG and the incidence of NPG was more frequent in cancer≤20 mm. However, there was no difference in terms of clinicopathologic characteristics between PG and NPG.
In conclusion, small advanced CRC may have the same malignant potential as ordinary advanced CRC so they should not be ignored.