Hyperplastic polyps of the colon and rectum. An immunohistochemical study with monoclonal antibodies against blood groups antigens (Sialosyl-Le^a, Le^b, Le(x), Le(y), 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-Le^a, Le^a, Le^b, Le(x), Le(y), A, B, and H. Sialosyl-Le^a, Le^a, Le(x), and Le(y) can be thought 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 Le^b are not expressed in the normal distal colon, however, they are extenively expressed on distal colorectal cancers and andenomas and can be considered onocofetal BGA. HP expressed Le^a, Le(x), Le(y) in the same compartment of the crypt as normal colon and extensively expressed Sialosyl-Le^a 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 Le^b and 5 of 50 HP expressed A BGA. Of the 6 HP expressing Le^b 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-Le^a 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 onocofetal BGA. These data suggest that the lesions classified morphologically as HP may be antigenically heterogenous.