Neurofibromas are benign tumours found on or within the body. All Neurofibromas grow from the tissue surrounding a nerve fiber. Neurofibromas generally appear in late childhood or early adolescence when hormones can affect the growth rate. They can be small, pea sized lumps or up to several centimeters in size.
Cutaneous or Dermal Neurofibromas are found on or under the skin. They are slow growing, usually soft and malleable (moveable), and can look smooth or like a collection of bumps.
Subcutaneous Neurofibromas are found deeper in the body and are firmer to the touch. Discrete neurofibromas are encapsulated, meaning they have definite edges or borders. Most people with NF1 have only several neurofibromas, but more rarely, some people can have hundreds or thousands of them, most commonly on the chest, arms and back. While they can be disfiguring if they appear on the face, neurofibromas are generally only removed it they cause concern or pain or are in an inconvenient location (e.g. under a bra strap).
It is extraordinarily rare for a discrete neurofibroma to become cancerous. However, they may have a detrimental impact on body systems by pressing on bone, nerves or other tissue, but will not invade these other structures. On the other hand, plexiform neurofibromas can wrap themselves around blood vessels and nerves and can therefore be more difficult to treat. (see Plexiform neurofibroma)