In the epithelioid histopathologic subtype of MPNST, a rare tumor with diffuse S-100 positivity, infrequent association with NF1, and occasional malignant transformation from schwannoma, mutations in SMARCB1 have also been observed in two-thirds of patients evaluated (n = 63) [62]. This evidence concerns the gene NF1 and malignant peripheral nerve sheath tumor.