To clarify the biologic significance of esophageal squamous epithelial dysplasia, especially the similarity to carcinoma in situ, immunohistochemical investigation of HLA-DR antigen expression and lymphocyte infiltration was performed. HLA-DR antigen was expressed in 12 of the 35 invasive carcinomas (34.4%), 23 of the 38 intraepithelial carcinomas (60.5%), 21 of the 50 areas of dysplasia (42.0%) and only 2 of the 625 specimens of non-cancerous squamous epithelium (0.3%). The HLA-DR-positive rate of dysplasia localized continuous to HLA-DR-positive carcinoma was 68.4%, which was significantly higher than that for HLA-DR positive dysplasia localized continuous to HLA-DR negative cancer (11.1%) (p<0.05). In areas of dysplasia and intraepithelial carcinoma, T cell infiltration was significantly increased at the sites of HLA-DR antigen expression (P<0.01). B cell infiltration was also more common in areas of positive expression. These results suggest that HLA-DR antigen is associated with the local immune response to squamous epithelial dysplasia, and that HLA-DR antigen expression may prevent tumor invasion similarly to its role in intraepithelial carcinoma.

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