HNC may also carry somatic mutations in PIK3R1 (~7%) and PTEN genes (51, 119), with loss of function in approximately 30% of HNC (more common than other cancers) due to mutations, loss of heterozygosity in the 10q region (which includes PTEN), detected in more than 70% of HNSCC, or hypermethylation, reported in ∼5% of these. Here, PTEN is linked to head and neck squamous cell carcinoma.