[Immunohistochemical studies on Lewis blood group antigens in carcinomas and adenomas of the sigmoid colon and rectum].

The presence of Lewis blood group antigens (Lewis(a), Lewis(b)) was determined immunohistochemically in 75 carcinomas and 58 adenomas of the sigmoid colon and rectum. 1. The rate of positive Lewis(b) staining of adult normal mucosa was 100% in the ascending colon, 100% in the transverse colon, 25% in the sigmoid colon and 30% in the rectum, respectively. The incidence of Lewis(b) was high in the proximal colon but low in the sigmoid colon and rectum. 2. The rate of positive Lewis(b) staining was 97% in cancer, 57% in adenoma and 26% in normal mucosa, respectively. The difference between the incidence of positive Lewis(b) staining in normal mucosa, and those in cancer and adenoma was significant (p less than 0.01). 3. The rate of positive Lewis(b) staining was 42% in mild and moderate dysplastic adenoma and 68% in severe dysplastic adenoma. There was a significant difference between the percentage of Lewis(b) staining in mild or moderate dysplastic adenoma and that of severe dysplastic adenoma (p less than 0.05). The expression of Lewis(b) antigen correlated with the size of adenoma. These results suggest that Lewis(b) antigen has a cancer-associated nature and Lewis(b) staining might be useful as an indicator of malignant potential of adenoma of the sigmoid colon and rectum.