Of these, HER2 dimerizes with other members of the HER family, and the dimerization of HER2:HER3 dimers was proven to be the most oncogenic receptor pairing that activates the RAS–RAF–MEK and PI3K–AKT–mTOR pathways in HER2-positive breast cancer cells (35). The gene discussed is PIK3CA; the disease is breast carcinoma.