PTEN and squamous cell carcinoma: Studies have shown that inactivation mutation of the tumor suppressor gene phosphatase and tensin homolog (PTEN), in association with other epigenetic changes, leads to increased activity of phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway, which is found in most squamous cell carcinomas of the head and neck region (Squarize et al., 2013).