RNA sequencing detected a novel in-frame fusion gene, ESR1-ARMT1, between ESR1, encoding estrogen receptor 1, and ARMT1, encoding acidic residue methyltransferase 1, in an ER+ luminal type invasive ductal carcinoma, case BR15-035T (Supplementary Figure 2). The gene discussed is ESR1; the disease is invasive ductal breast carcinoma.