ERBB2 and breast cancer: First, Hennessy et al. [11] compared the transcriptional profiling of metaplastic breast cancers (MBCs), which are an aggressive and chemoresistant subgroup of TNBCs, with other common breast cancer subtypes including luminal, HER2-enriched and basal-like cancers and identified that MBCs are the most related to the recently identified claudin-low breast tumors.