P53 GENE ALTERATIONS AND P53 PROTEIN ACCUMULATION IN INFILTRATING DUCTAL BREAST CARCINOMAS - CORRELATION BETWEEN IMMUNOHISTOCHEMICAL AND MOLECULAR-BIOLOGY TECHNIQUES

One hundred and eighty-eight infiltrating ductal carcinomas of the bre ast were examined immunohistochemically (IMM) for p53, and the results were compared to those of single strand conformation polymorphism (SS CP). Of the 65 IMM+ cases (35%), 32 showed a genetic alteration in exo ns 5 to 9. In some of the IMM+ SSCP- cases, the number of 53+ cells in the tumor was too low to be detected by SSCP. Cases with only a few p 53+ cells must not necessarily be considered negative, because a genet ic alteration has been found in nine such cases. However, in a few cas es, the accumulation of p53 protein could be caused by a factor other than mutation. Of the 123 IMM- cases, six showed gene polymorphism. p5 3 phenotype, as established with three monoclonal antibodies, did not correlate with genetic alteration in a particular exon. p53 IMM+ or SS CP+ tumors were generally ER-, grade III tumors and were uncommon in w omen older than 69 yr of age. The two methods have almost the same pro gnostic value. The accumulation of p53 protein is a good indicator of p53 mutation and therefore, immunohistochemistry remains a good method for the detection of such mutations.