Loss of ARID1A expression can also be a result of ARID1A promoter hypermethylation [20], and it is likely that tumors use sequence mutations in both alleles, or promoter hypermethylation together with mutations in different alleles, to drive complete loss of ARID1A proteins, following the classical “two-hit” theory characterizing tumor suppressor genes. This evidence concerns the gene ARID1A and neoplasm.