A 41-year-old woman has had diminished hearing for the past 4 months. On physical examination, she has decreased hearing on the left. Sound lateralizes to the right ear on the Weber tuning fork test. A head MRI shows a sharply circumscribed, 4-cm mass adjacent to the left pons that extends toward the left inferior cerebellar hemisphere. A smaller 1-cm lesion is in a similar location on the right. Family screening reveals a similarly affected 38-year-old sibling. An inherited mutation involving which of the following genes is most likely to be present in this patient?

A schwannoma in this location also is known as a cerebellopontine angle tumor. Schwannomas in this location arise from cranial nerve VIII; they are also called acoustic neuromas. Most schwannomas act as benign, slow-growing tumors that can be completely resected. Having bilateral acoustic schwannomas is virtually pathognomonic for neurofibromatosis type 2. Other familial tumor syndromes involving the brain include Li Fraumeni syndrome with p53 mutations and medulloblastomas, Gorlin syndrome with PTCH mutations and medulloblastomas, tuberous sclerosis with TSC1 mutations and cortical hamartomas, and von Hippel-Lindau syndrome with VHL mutations and hemangioblastomas.