SMARCB1 and schwannoma: However, the lack of involvement of the SMARCB1 gene (neither LZTR1) in the lost 22q12.1q13.33 region, together with the identification by SNP-array analysis of the same breakpoint in both schwannomas, pointed to this molecular event as the first hit occurring in at least the schwannoma-initiating cells present in this limb segment of the patient.