Abstract
The expression of the HLA‐DR antigen, a Class II HLA antigen, was analyzed in 41 cases of gastric carcinoma (23 intestinal‐type and 18 diffuse‐type according to a modified Lauren classification) using a monoclonal antibody that is reactive to this antigen in routinely formalin‐fixed, paraffin‐embedded tissue sections. Seventeen cases of intestinal‐type gastric carcinoma and two cases of diffuse‐type gastric carcinoma were positive for the HLA‐DR antigen. The staining in intestinal‐type carcinoma generally was stronger and more extensive than in diffuse‐type carcinoma, which showed only weak and focal staining. The difference in the frequency and pattern of staining between intestinal and diffuse‐type gastric carcinoma supports the concept that these are two distinct subtypes of gastric carcinoma.