TP53 and invasive breast carcinoma: Similar to our findings, Mdm2 nuclear staining was relatively frequent in BrCa biopsies (>50%)25 and also in ~40% of benign BrCa cases.26 However, deregulated Mdm2 linked to estrogen in this BrCa context cannot account for low p53 levels (as reported for MCF7, where estrogen-induced elevated Mdm2 did not correlate with reduced p53).27