The main signalling pathways mediated by HER2 involve rat sarcoma (RAS)/rapidly accelerated fibrosarcoma (RAF)/mitogen-activated protein kinase (MAPK) pathways and phosphoinositide-3-kinase (PIK3)/protein kinase B (Akt)/mechanistic target of rapamycin (mTOR) kinase pathways, which regulate growth, proliferation, differentiation, motility, and adhesion of normal cells [5]. The gene discussed is AKT1; the disease is fibrosarcoma.