Therefore, the somatic activating mutations in exon3 of CTNNB1 (encoding β-catenin) can cause stabilization of β-catenin, which lead to β-catenin accumulation in the nucleus.Theoretically, the immunohistochemical accumulation of β-catenin in the nucleus can be used to identify WNT-activated MBs. This evidence concerns the gene CTNNB1 and Mobius syndrome.