HER2 related tumor subtypes are characterized by basal and luminal features. (A) Heatmap showing the expression level of basal-type specific genes in subgroups 7 and 10 tumors. (B) Subgroup 10 tumors show significantly higher GATA3 mRNA expression (P = 0.0008) as compared to subgroup 7 tumors. (C) Subgroup 10 cell lines (HCC202) demonstrate higher levels of GATA3 expression than subgroup7 cell lines (AU565). (D) Validation of the luminal-basal signatures demonstrates an accurate prediction of basal (mean predicted probability: 0.933) and luminal (mean predicted probability: 0.321) breast tumors (P <0.0001). (E) Validation of luminal-basal signature in validation dataset shown accurate prediction of basal (mean predicted probability: 0.992) and luminal (mean predicted probability: 0.438) tumor status. (F) HER2 related tumors from the primary dataset of 1,143 samples in subgroup 7 demonstrate basal-like features while subgroup 10 tumors are associated with luminal-like features (P <0.0001). (G) HER2 related tumors in the validation dataset show significant enrichment of basal and luminal features in subgroups 7 and 10, respectively (P <0.0001). (H) Validation of subgroup 7/10 signature to predict subgroup7 and 10 characteristics of tumors assigned to subgroup 7 (mean predicted probability: 0.7950) and subgroup 10 (mean predicted probability: 0.2022) with a congruency rate of 84.5% (P <0.0001). (I) Classification of basal and luminal breast cancer cell lines demonstrates a congruency of 72% with basal and luminal status (P <0.0001).