Further, they are classified into four different molecular subtypes, namely luminal A (ER+/PR+ and Ki67 high), luminal B (ER+/PR+, Ki67 low or ER+/PR+/HE R2+), HER2 (HER2+) enriched, and basal types, as well as more significant microbial features in the tumor microenvironment of BCs as compared with that of healthy breast tissues. The gene discussed is ESR1; the disease is neoplasm.