ESR1 and breast carcinoma: Other main targets include EGFR NP_005219.2:p.C797S or MET proto-oncogene, receptor tyrosine kinase (MET) amplifications as osimertinib resistance-causing variations [43], various ALK receptor tyrosine kinase (ALK) mutations in NSCLC patients under ALK inhibitors [44,45], or of phophatidylinositol-4,5-biphosphate 3-kinase catalytic subunit alpha (PIK3CA) or estrogen receptor 1 (ESR1) variations in breast cancer patients under hormonal or endocrine treatment regimens [46,47].