We found an unexpectedly large number of genes differentially expressed during breast cancer progression across subtypes: in luminal tumors, 55% of measured transcripts were dynamically differentially expressed during progression (31 296 out of 56 830 transcripts measured by TCGA consortium); in HER2‐enriched tumors, 31% were dynamically differentially expressed (17 827 transcripts); and in basal‐like tumors, 32% were dynamically differentially expressed (18 505 transcripts). Here, ERBB2 is linked to breast cancer.