Luminal-A (LUM-A) are ER and/or PR positive, HER2 negative and have low proliferation markers such as Ki-67; luminal-B (LUM-B) are ER positive and/or PR positive, and either HER2 positive or negative with higher levels of Ki-67; her 2 enriched is ER and PR negative and HER2 positive; triple-negative/basal-like breast cancer (TNBC) is defined as ER and PR negative, and HER2-negative; LUM-A cancers are low-grade, tend to grow slowly and have the best prognosis, whereas LUM-B cancers generally grow slightly faster than LUM-A cancers and their prognosis is slightly worse. Here, ESR1 is linked to cancer.