SMARCB1 and leiomyoma: This 4-hit/3-step model of tumorigenesis probably also holds true for other benign tumours observed in patients with SMARCB1-positive schwannomatosis, since biallelic inactivation of SMARCB1 and NF2 has been observed in a meningioma and leiomyoma of patients with germline SMARCB1 mutations (van den Munckhof et al. 2012; Hulsebos et al. 2014b).