In particular, the mutation and down- or upregulation of molecular mechanisms such as PI3K/Akt/mTOR (mammalian target of rapamycin), TP53, NOTCH, EGFR, JAK/STAT, Ras/MEK/ERK, and MET pathways are found to be associated with the progression of H&N squamous cell carcinoma (20) (Figure 2D). The gene discussed is PIK3CA; the disease is squamous cell carcinoma.