ESR1 and breast cancer: Since GATA3-AS1 is consistently expressed in luminal B patients according to different studies [27,57] and was found to be associated with the RD after NAC in this group of patients, we aimed to detect GATA3-AS1 expression using RNA-ISH technology; this approach involves the use of histological slides, and is similar to the approach used to detect estrogen receptor, Ki67, and HER2 expression in breast cancer laboratory tests [8,49,51].