ERBB2 and breast neoplasm: Several additional classifications using mathematical Topological Data Analysis (TDA gene expression signature) led to the proposition of seven breast tumor subtypes: (Basal/HER2, LumB/Basal, LumA, Basal/Myoepithelial (Myo), Myo/LumA, Myo/LumB and Myo/LumB/HER2) [5].