RESUMO
The expression of HLA-DR antigen was analyzed in formalin- fixed paraffin-embedded sections of 218 normal and abnormal thyroid specimens. The specimens were selected from the biopsies received at the Pathology Laboratory over a period of 5 years. Sections were stained by H and E and immunoperoxidase technique using Avidin Biotin Conjugate method for a monoclonal antibody, HLA-DR-chain. Positivity for HLA-DR was detected in all cases of thyroiditis, in 84% of Graves' disease and in 80.8% of papillary carcinoma. HLA-DR was found in thyroid epithelial cells, lymphocytes and in vascular endothelial cells. On the other hand, thyroid epithelial cells in all cases of normal thyroid, simple goitre, cretinism with goitre, thyroid adenomas, follicular and anaplastic carcinomas showed no reactivity for HLA-DR. These results indicated that epithelial cells from thyroids of patients with autoimmune diseases commonly express HLA-DR antigen. Also, the presence of HLA-DR antigen in most papillary thyroid carcinomas may be helpful diagnostically in cases of follicular variant of papillary carcinoma