Immunohistochemical detection of ras oncogene p21 product in benign and malignant mammary tissue in man.

The monoclonal antibody RAP-5 generated against a synthetic peptide corresponding to amino acid positions 10-17 of the ras p21 protein was used in an immunohistochemical study of the expression of ras in normal, benign, and malignant breast epithelium in man. The staining intensity and intracellular distribution of RAP-5 was similar in the three epithelial populations and extended to other tissue elements including myoepithelial cells, smooth muscle, myelin, capillary endothelium, and stromal fibroblasts, as well as sebaceous glands and sweat glands overlying the breast. These results suggest that RAP-5 recognises a normal cellular component, the expression of which is not more enhanced in hyperplastic or neoplastic conditions. The detection of mutant forms of p21 exclusively expressed in malignant tumours requires that alternative reagents be developed.