Hyperplastic polyps of the colon and rectum. An immunohistochemical study with monoclonal antibodies against blood groups antigens (sialosyl-Lea, Leb, Lex, Ley, A, B, H).

We studied 40 hyperplastic polyps (HP) immunohistochemically with monoclonal antibodies against 8 different blood group antigens (BGA) comparing their reactivity with normal control colon and colorectal adenocarcinomas. The 8 BGA studied were: Sialosyl-Lea, Lea, Leb, Lex, Ley, A,B, and H. sialosyl-Lea, Lea, Lex, and Ley can be though of as differentiation antigens. The former 2 BGA are expressed on mature (differentiated) epithelium while the latter 2 BGA are expressed by undifferentiated epithelium of the crypt base. A, B, H and Leb are not expressed in the normal distal colon, however, they are extensively expressed on distal colorectal cancers and adenomas and can be considered oncofetal BGA. HP expressed Lea, Lex, Ley in the same compartment of the crypt as normal colon and extensively expressed Sialosyl-Lea throughout the entire length of the crypt. This latter finding indicated maturation at a lower point in the crypt than in normals. All HP failed to express B and H BGA, while 6 of 40 expressed Leb and 5 of 40 HP expressed A BGA. Of the 6 HP expressing Leb BGA, 3 were from patients with synchronous or metachronous cancers and 2 from patients with mixed hyperplastic polyp-adenomas (HP/AD). Two of the HP expressing A BGA were from patients with HP/AD. The expression and distribution of these BGA in HP, especially the extensive expression of sialosyl-Lea correlates with the known cell kinetics of HP. While nonneoplastic in nature, HP may occasionally express true oncofetal BGA. Similarly, the HP component of HP/AD may also express true oncofetal BGA. These data suggest that the lesions classified morphologically as HP may be antigenically heterogenous.