As shown in Fig. 1b, ID4 expression is significantly lower in luminal A (n = 434) and luminal B (n = 194) subtypes (both ER+) as compared with basal-like (n = 142) and normal-like breast tumors (n = 119) (both ER−) (p < 0.001). The gene discussed is ESR1; the disease is breast neoplasm.