Neurofibromas of the Skull
Neurofibromas are tumors that arise from the outer sheath of peripheral and cranial nerves. Although neurofibromas may arise sporadically, 90% of neurofibromas are asosociated with neurofibromatosis type I, an autosomal dominant neurocutaneous disorder associated with tumor development throughout the central and peripheral nervous system. Peak presentation is between 20 and 30 years of age, and both males and females can be equally affected. Most neurofibromas are benign tumors, however 5-10% of large neurofibromas may undergo malignant transformation into malignant peripheral nerve sheath tumors (MPNSTs). Cells harboring the NF-1 mutation undergo inactivation of the gene encoding neurofibromin, leading to unregulated cell growth via the RAS pathway. A subset of neurofibromas, known as plexiform neurofibromas, are more locally invasive and aggressive, and are associated with worse clinical outcomes.