The gene abnormalities covered by our BC-monitor are important in practice; many of them indicate a poor prognosis (MET, CDH1, TP53, PIK3CA, ESR1, and HER2); the presence of resistance mechanisms (PIK3CA, ESR1, HER2, and FGFR1); or represent druggable targets (PIK3CA, ESR1, HER2, and AKT1) at the same time. The gene discussed is PIK3CA; the disease is breast cancer.