NF1 and neoplasm: NF-1 is caused by heterozygous pathogenic variants of the NF1 tumor suppressor gene on chromosome 17q11.2, resulting in the constitutive activation of the RAS pathway via MEK, which is implicated in cell proliferation and promotes tumor growth and progression.3,4) PNs, which are histologically benign nerve sheath tumors, are the most frequent tumors associated with NF-1.