Distribution of blood group antigens and CA 19-9 in gastric cancers and non-neoplastic gastric mucosa.

The distribution of blood group ABH antigens, their precursor I(Ma) antigen, Lewis a antigen and monoclonal antibody-defined tumor-associated antigen CA 19-9 in gastric cancers and their surrounding non-neoplastic mucosa was studied by using immunohistochemical methods. ABH antigens were localized in the foveolar epithelium except for a few cases presumed to be non-secretors, but ABH antigens were lost focally from metaplastic mucosa. In contrast, Lewis a and I(Ma) antigens were present in the foveolar epithelium of non-secretors and metaplastic mucosa where ABH antigens were not detected. Gastric cancers also showed focal loss of ABH antigens and gain of Lewis a and I(Ma) antigens, and the cancer cells showed marked heterogeneity in antigen expression compared with non-neoplastic mucosa. Expression of incompatible blood group antigen (A-like antigen) reactive with monoclonal anti-A antibody was also detected in cancer cells of blood group O and B cases. CA 19-9 (sialylated-Lewis a) was detected in 62% of gastric cancers and in the restricted areas of gastric mucosa where Lewis a was positive.