Blood group substances as tumor antigens in the distal colon.

Adenocarcinomas of the sigmoid colon and rectum were studied for the presence of blood group substances of the A, B, H system using the method of specific erythrocytic adherence. Of 17 adenocarcinomas studied, eight were found to have reactivity for blood group substances. All eight tumours showing reactivity for blood group substances were from patients of the blood group type A, whereas no blood group substances reactivity could be found in any of the adenocarcinomas from patients of the B blood group type. The epithelial cells of the entire colon contain blood group substances in the fetal period; however, shortly after parturition the epithelial cells of the distal colon and rectum rapidly lose the substances. The reappearance of the substances in adenocarcinomas of the distal colon suggests that these neoplastic cells are expressing certain characteristics of fetal colonic epithelial cells.