NF1 and malignant peripheral nerve sheath tumor: In addition, homozygous deletion of the CDKN2A/B cell cycle regulator is a notable frequent and likely early initiating copy number alteration event seen in ANNUBP and MPNST.2,18–29 Across studies, CDKN2A/B deletion is typically the only other genomic alteration noted aside from the loss of chromosome 17q and NF1 gene expression in ANNUBP.