It is very critical to improve the identification accuracy of the PAM50 subtypes in clinical diagnosis, since the currently widely used IHC-based alternative subtyping uses the expression levels of only four IHC markers (ER, PR, HER2, and Ki67), whereas the PAM50 subtyping system is able to portray the typical and comprehensive transcriptomic characteristics of BC. The gene discussed is ESR1; the disease is breast cancer.