ESR1 and breast cancer: These tumors displayed characteristics of aggressive BC associated with poor prognosis, including (1) a predominant basal-like subtype (Fig. 1 D and Table S2); (2) hormone receptor (estrogen receptor [ER] and progesterone receptor [PgR])–negative status (Fig. 1 E and Table S2); and (3) enrichment of p53 mutations/deletions or Myc amplification (Fig. 1 E and Table S2; Deming et al., 2000; Green et al., 2016; Miller et al., 2005).