Geisler et al. demonstrated that nearly 30% of all mutations in primary breast cancer, in particular those of the nonsense type, are not detected by IHC and that most studies evaluating p53 status by IHC have failed to show a predictive value of p53 for chemotherapy, whereas studies evaluating p53 status by DNA sequencing have reported mutations that predict resistance to chemotherapy [15]. The gene discussed is TP53; the disease is breast carcinoma.