[Immunohistochemical study on HLA expression of human breast cancer]

One hundred and nine cases of breast cancer were examined by immunoperoxidase staining of frozen section for their HLA expression. Sixty one cases (56%) were negative or very weak for HLA class I expression, while normal mammary ductal epithelia showed intense positivity in both class I and class II antigens. The extent of expression correlated well with the histopathological subtyping of invasive ductal carcinoma in Japan, which reflects the prognosis quite well. Degree of lymphoid cell infiltration was also proportional to HLA expression by tumor cells. It may be that lack of HLA antigen expression leads to failure of induction of cytotoxic T cells, thus modulating the immunological response and influencing prognosis.