The key genes identified for luminal A breast cancer were GRM4, GRM8, KRT18, NMUR1, MUC1, CX3CL1, GATA3, and NCAM1. The neuroactive ligand–receptor interaction pathway was enriched for GRM4, NMUR1, and GRM8 (P < 0.05). The gene discussed is GRM4; the disease is breast carcinoma.