Distribution comparison of depressed vs. non-depressed early colorectal cancers

Background Colorectal depressed tumours have a tendency to invade deeper mucosal layers and metastasize in the lymph nodes, despite their small size. Aim To investigate the clinical and endoscopic characteristics of depressed early colorectal cancers (intramucosal and submucosal adenocarcinoma) compared with non-depressed early cancers. Methods Five hundred and seventy consecutive early colorectal cancers obtained through endoscopic resection or surgical operation were studied. Early cancers were endoscopically classified as either the depressed or non-depressed type. The age and gender of the patients as well as the size and distribution of the cancers were compared between types. The tumour locations were classified into three groups: caecum to transverse colon (right colon), descending to sigmoid colon (left colon) and rectum. Results Patients were similar with respect to age and gender. The mean size of the depressed type was smaller than that of the non-depressed type (mean 8.4 mm vs. 13.3 mm; P < 0.0001). The rate of occurrence of depressed type in the right colon was higher than that of non-depressed type (49% vs. 23%) (P = 0.0006). Among the early cancers, the incidence of the depressed type in the right colon was higher than that in the left colon and rectum (15% in the right colon, 7% in the left colon and 4% in the rectum; P < 0.01). Conclusions Compared with non-depressed early colorectal cancers, depressed cancers were smaller in size and more likely to be distributed in the right colon.