HLA-C and breast neoplasm: The reactivity of murine monoclonal antibodies (McAbs) directed against the monomorphic determinants of Class I and Class II antigens of the major histocompatibility complex (MHC), and against antigens expressed by discrete populations of leucocytes was studied using the indirect immunoperoxidase technique on serial tissue sections of 16 benign and 17 malignant primary human breast tumours.