This suggests a 4-hit, 3-step model of tumorigenesis, in which the mutated germline SMARCB1 gene copy is kept in the tumor (hit 1), the totality or part of chromosome 22 containing the wildtype SMARCB1 gene copy and a wildtype copy of the NF2 gene is lost (hits 2 and 3), followed by an alteration in the remaining wildtype NF2 gene copy (hit 4). Here, NF2 is linked to neoplasm.