B1/P/Rbf tumors had increased expression of genes that were previously identified as upregulated in the luminal subtype of BC [35], including Esr1 (estrogen receptor), Krt19 (cytokeratin 19), zinc finger transcription factor Gata3 and Forkhead box protein A1, Foxa1 (Fig. 4D). Here, ESR1 is linked to breast cancer.