An immunohistochemical validation of basal-like breast cancer by Nielsen et al. showed that the microarray-defined basal-like breast cancer could be effectively identified using a panel of four immunohistochemical markers (ER-, HER2-, CK 5/6+ and HER1+) with 100% specificity and 76% sensitivity [9]. The gene discussed is ERBB2; the disease is breast carcinoma.