Using molecular profiling to investigate the variable prognosis and response to therapy of HER2+ tumors, Staaf et al. [23] identified a 158-gene HER2-derived prognostic predictor (HDPP) that improved the stratification of good and poor prognosis for both OS and distant metastasis-free survival in both the HER2-enriched molecular subtype and the basal-like subtype, which are assumed to be mutually exclusive breast cancer entities. Here, ERBB2 is linked to breast cancer.