After EGFR binds to HER2 to form EGFR-HER2 heterodimers, it triggers receptor conformational changes, activates intracellular tyrosine kinase domains, significantly enhances downstream signals (such as MAPK, PI3K-AKT pathways), and promotes tumor cell proliferation, survival and metastasis (19). The gene discussed is PIK3CA; the disease is neoplasm.