Neurofibromas are benign or non-cancerous tumors that grow on nerves throughout the body. While they are seen in people without NF1, the presence of two or more of these tumors should raise the suspicion of NF1. There are three major types of neurofibroma: cutaneous, spinal and plexiform.
Cutaneous neurofibromas are also called discrete or dermal neurofibromas. These tumors grow from small nerves in the skin or just under the skin and appear as small bumps typically beginning around the time of puberty. It is less common to see this type of neurofibroma in young children with NF1. Individuals with NF1 commonly develop more cutaneous neurofibromas as they get older. In addition, women often notice that during pregnancy they develop more neurofibromas or that existing neurofibromas grow larger. Cutaneous neurofibromas rarely cause medical problems but may itch or be tender when bumped. It is important to note that these tumors remain benign throughout life and do not become malignant cancers. Despite their benign nature, they may cause significant cosmetic problems and occasionally may require removal.
Spinal neurofibromas are typically larger tumors that grow from nerves along the spinal column in adults with NF1. Despite the fact that spinal neurofibromas are close to the spinal cord, most people with spinal neurofibromas experience no medical problems as a result of their growth. Occasionally, adults with NF1 will experience back pain, numbness in an arm or leg and minor weakness. People who develop these symptoms should consult a physician who is an expert in NF1.
Plexiform neurofibromas are larger, more extensive tumors that grow from nerves anywhere in the body. Unlike cutaneous neurofibromas, plexiform neurofibromas are often found in young children, sometimes even present around the time of birth. Plexiform neurofibromas may be located around the eye socket, face, arm, leg, back, chest, or abdomen. Unlike cutaneous neurofibromas, plexiform neurofibromas do not always stay benign throughout life. Uncommonly, a plexiform neurofibroma may change into a cancer, called a malignant peripheral nerve sheath tumor (MPNST). There are no reliable tests to screen for an MPNST. However, people with plexiform neurofibromas should promptly consult a NF1 specialist if they experience continued pain in their tumor (not associated with it being hit or bumped), rapid tumor growth, hardening of their tumor, or weakness or numbness in an arm or leg with a plexiform neurofibroma. These are signs that the plexiform neurofibroma may have changed into a cancer.