Immunohistochemical study of the ras oncogene expression in human breast lesions.

An immunohistochemical study of ras oncogene expression in human breast lesions was carried out using a monoclonal antibody, Y13 259, to the ras encoded p21 protein. A total of 75 cases of breast disease examined included: 33 simple and complex cystic disease; 22 simple and hyperplastic fibroadenomas; 18 ductal, lobular and mixed carcinomas and 2 in situ carcinomas. Most of the complex cystic disease, hyperplastic fibroadenomas and all types of carcinomas showed high p21 expression as indicated by staining intensity. These results suggest that elevated ras expression may play an important role in the development of some premalignant and malignant breast lesions.