PURPOSE:Recent advances have made possible the treatment of small invasive colorectal cancer by means of polypectomy or endoscopic mucosal resection. CD44 expression in cancer cells was identified as an indicator of lymph‐node metastasis, which could be evaluated in specimens removed by colonoscopy.METHODS:The correlation between lymph‐node metastasis and the expression of standard‐type CD44 in cancer cells was examined immunohistologically using the invaded cancer cells of 61 tissue samples of superficially invasive colorectal cancer. We defined the above as invasive cancer restricted within the colorectal wall. Of the 61 samples, 31 had submucosal invasion and 30 had muscular invasion.RESULTS:Standard‐type CD44 expression in the area of invasion in cases with lymph‐node metastasis was remarkably down‐regulated. In 43 cases with no lymph‐node metastasis, 36 (83.7 percent) of patients had CD44 expression in invaded cells, whereas only two of 18 cases (11.1 percent) with lymph‐node metastasis had expression of standard‐type CD44 in the same area (P<0.0001). A total of 69.6 percent (16/23) of patients with loss of standard‐type CD44 expression in invaded sites were found to have positive metastasis in the lymph nodes. These results suggest that standard‐type CD44 in invasive colon cancer cells could suppress metastasis to the regional lymph nodes.CONCLUSION:In cases of invasive colorectal cancer, the loss of standard‐type CD44 expression in the invaded area is a sensitive marker for metastasis to the lymph nodes. Further investigation with larger patient groups is required to clarify the reliability of loss of standard‐type CD44 expression as an indicator for additional surgery after endoscopic resection of submucosal invasive colorectal carcinoma.