Pathways downstream of receptor tyrosine kinases that are often implicated in endocrine resistance and have been investigated for the treatment of endocrine-resistant breast cancer include the MAPK signaling pathway and the PI3K/AKT pathways as well as their shared downstream mechanistic target of rapamycin (mTOR) complex and CDK4/6. This evidence concerns the gene NTRK1 and breast carcinoma.