Location of early colorectal cancers at fold-top may reduce the risk of lymph node metastasis.

PURPOSE

This study was designed to look for significant correlations between location of early colorectal cancer, distance from muscularis mucosae to muscularis propria, and the frequency of lymph node metastasis.

METHODS

A total of 166 early colorectal cancers, including 67 surgically resected lesions, were evaluated. The cancers were divided into two groups: metastatic and nonmetastatic. Cancer lesions were further subtyped at the fold-top or fold-bottom. Macroscopic classifications and histology were performed. Absolute invasive depth and distance from muscularis mucosae to muscularis propria was measured. Multivariate analysis was used to assess relationships among the variables.

RESULTS

The percentage of polypoid cancer lesions at fold-bottom was higher than at fold-top (74.5 vs. 51.8 percent), whereas flat-type cancer lesions at fold-bottom occurred less often than at fold-top (8.2 vs. 30.4 percent). Logistic regression showed that deep absolute invasive depth, lymphatic and vessel invasion, and cancer location (at fold-bottom) were the significant risk factors for early colorectal cancers leading to lymph-node metastasis. The distance from muscularis mucosae to muscularis propria with lymph-node metastasis (1,396.7 +/- 728.4 microm) was shorter than without lymph-node metastasis (3,533.9 +/- 2,507.8 microm; P < 0.01). Multivariate analysis showed that distance from muscularis mucosae to muscularis propria was a statistically significant factor for early colorectal cancers leading to lymph node metastasis (P = 0.0054).

CONCLUSIONS

We conclude that early colorectal cancers at the fold-top or with a long distance from muscularis mucosae to muscularis propria have less tendency to metastasize to lymph nodes. Clinically, these results provide evidence of a new indicator of endoscopic mucosal resection for early colorectal cancers at the fold-top.