Breast cancer has several molecular target pathways, including the EGFR Family, the vascular endothelial growth factor (VEGF) family, the RAS/MEK/ERK Pathway, cell cycle and apoptosis, estrogen receptor (ER) antagonist, targeting invasion and metastasis, insulin-like growth factor inhibitors, and the steroid hormone receptor. The gene discussed is ESR1; the disease is breast carcinoma.