In epithelial-origin cancers, EBV infection has been strongly associated with the gain of CpG methylation, and methylation of tumor suppressor genes such as p14, p16, IHH, TRADB, PTEN or SSTR1 is likely the key mechanism of oncogenesis [19,21,22,76]. The gene discussed is PTEN; the disease is Epstein-Barr virus infection.