SMARCB1 variant-positive schwannomatosis is thought to involve a four-hit, three-step model of tumorigenesis, where the initial SMARCB1 variant triggers partial loss of chromosome 22 containing the wildtype SMARCB1 and NF2, and finally followed by a spontaneous mutation in the remaining wildtype NF2 [31]. The gene discussed is NF2; the disease is schwannomatosis.