Usefulness of dilated blood vessels in the tumor periphery for assessing the invasion depth of small-sized depressed colorectal cancer

The relationship between dilated blood vessels in the tumor periphery and the tumor invasion depth is unclear. Therefore, the present study aimed to clarify the relationship between dilated blood vessels and the invasion depth of small-sized (<30 mm) colorectal cancer (CRC), and its implications on endoscopic treatment. We performed a single-arm observational study of the diagnostic accuracy of the existence of dilated vessels in the tumor periphery of CRC lesions as an indicator of submucosal deep (SM-d, ≥1000 μm) carcinomas. Lesions were classified into two groups based on the existence of dilated vessels by two experienced endoscopists. The clinicopathological features, invasion depth, and lymphovascular invasion/poorly differentiated clusters were analyzed in all resected specimens. Four hundred and two consecutive small-sized CRC lesions were included. The dilated vessels were observed in 96/402 (24%) lesions, and most of them (93/96) were found in depressed lesions. In depressed lesions, the histopathological diagnosis of the dilated vessels group showed SM-d or deeper invasion in 84/93 (90%) cases, whereas 3/20 (15%) had SM-d invasion in the nondilated vessels group (P < 0.001). When the dilated vessels were used as an indicator of SM-d or deeper invasion in depressed lesions, the sensitivity was 95.6%, specificity was 66.7%, and accuracy was 90.2%. No correlation was observed between the existence of dilated vessels and the lesion site, lesion diameter, and lymphovascular invasion/poorly differentiated cluster. The existence of dilated blood vessels in the tumor periphery suggests SM-d or deeper invasion in depressed lesions.