Monoclonal antibodies to the proteins of intermediate filaments and of basement membranes in the differential diagnosis of certain forms of human breast tumors

: Monoclonal antibodies to keratins No. 8 and 17 specific for lining epithelium and myoepithelium of the mammary gland, respectively, as well as to basement membrane laminin, entactin, collagen type IV and heparan sulfate proteoglycan were used to the immunohistochemical analysis of 77 benign and malignant human breast lesions and that of 38 cases in which an intraoperative biopsy diagnosis was difficult. Morphologically similar benign and malignant proliferations were distinguished by keratin expression. In benign lesions both keratins were present, while in malignant ones only keratin No. 8 was expressed. Basement membranes associated with a myoepithelial layer were intact in benign lesions and in situ structures, but they were absent around the vast majority of invasive tumor foci. Basement membrane loss was important in differential diagnosis of benign sclerosing adenosis and cystadenopapilloma from invasive tubular and papillary carcinoma, respectively. Diagnosis of microinvasion in ductal and lobular carcinoma was much easier when combination of antibodies to keratins and basement membrane proteins was used.