DIFFERENT PATTERNS OF HLA-DR ANTIGEN EXPRESSION IN NORMAL EPITHELIUM,HYPERPLASTIC AND NEOPLASTIC MALIGNANT LESIONS OF THE BREAST

Fifteen samples of non-tumoural breast tissue, 24 cases of benign lesi ons, four biopsies of inflammatory carcinomas and 94 tumour samples of primitive mammary carcinomas were analysed for HLA class II expressio n. We found, first, that HLA class II antigens were detectable in all cases of non-neoplastic breast tissue. Secondly, HLA class II antigen expression was notably increased in benign neoplasms and hyperplastic lesions. In contrast, only 32 out of 94 carcinomas showed expression o f HLA-DR antigens, 17 tumours had HLA-DP antigens and 11 carcinomas we re positive for the presence of DQ molecules. The expression of class II antigen was associated with the degree of histological differentiat ion (P < 0.05) but was independent of stromal leucocytic infiltration. Thirdly, HLA-DR was very strongly expressed in intravascular tumoural thrombi, especially in the 'inflammatory carcinomas'. The immunepheno type of inflammatory infiltrate was analysed in benign and malignant l esions. In malignant lesions the mean number of inflammatory cells was significantly higher than in benign lesions. Interestingly, we found no differences in the amount and composition of inflammatory infiltrat e between HLA-DR positive and negative tumours.