Monoclonal antibodies 323/A3 and Ca1 identify a paracrine function of breast carcinoma on adjacent benign histological components.

The 323/A23 monoclonal antibody (MAb) is expressed with increasing breast atypia, whilst Ca1 has been suggested as a marker of cancer risk in benign breast disease. To establish whether they would be useful as markers of malignancy the staining characteristics in benign tissue components associated with malignant biopsies have been compared with the staining patterns of benign biopsies from patients with no known malignancy. Staining with 323/A3 and Ca1 MAb was carried out on formalin-fixed paraffin-embedded tissue sections using ABC Vectastain Reagents (Vector Laboratories) and diaminobenzidine as the chromogen. All biopsies contained ductolobular tissues. Apocrine metaplasia was present in 35 of 79 malignant biopsies, in 42 of 77 selected and 20 of 50 prospective unselected benign biopsies. The 323/A3 MAb stained strongly the cytoplasm of apocrine metaplasia in breast carcinoma biopsies in 18 of 35 cases, in the selected benign group this was two out of 42 (P less than 0.001) and in the prospective benign group one of 19 (P less than 0.01). No differences in staining were noted for ductolobular tissue. The Ca1 MAb showed strong apical staining in ductolobular tissue in 66 of 79 invasive carcinoma biopsies, in 20 of 50 prospective benign biopsies and 53 of 77 selected biopsies. The prospective and selected benign group staining was significantly different from that of the invasive carcinomas (P less than 0.005 and less than 0.05 respectively). These data suggest that 323/A3 staining of apocrine metaplasia and Ca1 staining of ductolobular tissue is affected by a paracrine function of breast cancer.