What kinds of tumors occur in neurofibromatosis types 1 and 2?
Neurofibromatosis types 1 (NF1) and 2 (NF2) are genetic disorders of the autosomal dominant kind. The autosomal dominant label means that only one copy of a mutant gene is needed to produce the condition, and patients have a 50:50 chance of their children getting the disorder.
NF is a condition that produces tumors of the skin, internal organs, and nerves because normal genes that control cell growth are affected.
Neurofibromatosis type 1
NF1 skin tumors are very common and are called dermal neurofibromas. Surgical treatment is usually recommended for painful or irritating lesions. Neurofibromas are benign (not cancer), but there is a special type of neurofibroma called a plexiform neurofibroma.
Plexiform neurofibromas are deeper tumors that affect nerves. These tumors are usually followed without treatment although chemotherapy and surgery are options. With these types of tumors, there is a 5-10% risk of developing a malignant (cancerous) peripheral nerve sheath tumor.
Malignant peripheral nerve sheath tumors (MPNST) develop from plexiform lesions. The diagnosis is made by surgery. Treatment involves surgery, radiation therapy, and chemotherapy.
Gastrointestinal stromal tumors (GIST) develop in the small intestine. They can be treated with surgery. Several chemotherapy trials are under way.
Tumors can also develop in the eye (optic nerve glioma) and brain (astrocytoma). The grade of the tumor usually defines how fast it grows and how difficult it is to treat. Grade 4 astrocytomas are the most aggressive brain tumors and the most difficult to treat. If you are diagnosed with a brain tumor you should seek a specialist in neuro-oncology.
Neurofibromatosis type 2
NF2 usually causes more tumors affecting the brain and spinal cord. The classic findings are tumors (schwannomas) affecting the hearing nerve bilateral. Hearing loss is a significant risk. Treatment of these tumors can involve surgery or radiation therapy (possibly Gamma Knife®), depending on size and symptoms. Gamma Knife is a single high dose radiation delivered to the tumor.
Tumors affecting the spine are also common with NF2. The tumors can be in the spinal cord (intramedullary) or outside the spinal cord (extramedullary). Common types of intramedullary tumors include ependymomas and astrocytomas. Common extramedullary tumors include schwannomas and meningiomas. Meningiomas are tumors that arise from the meninges or covering of the brain and spine. Multiple meningiomas are seen in over 50% of NF2 patients. The above-mentioned may be treated with surgery, radiation therapy, or chemotherapy depending on a host of factors.
Outside the nervous system, the patient can develop pheochromocytomas (from adrenal glands); these increase blood pressure and heart rate. Patients may also develop carcinoid tumors, secreting hormones from the gut resulting in flushing and gastrointestinal symptoms. Since tumors can be a common finding in NF patients, be sure to discuss new or progressive symptoms with your physician.