Neurofibroma (including Plexiform), from the CureRays guide library.

Neurofibromas are usually benign tumors that grow on nerves; most need no treatment, larger or plexiform ones are watched or removed, and a newer targeted pill can shrink them — radiation is used sparingly because it can raise long-term risk in nerve-tumor syndromes.

What it is.

A neurofibroma is a tumor that grows from the cells that wrap and support nerves (the nerve sheath). The great majority of neurofibromas are benign, meaning they are not cancer and do not spread to other parts of the body. They can appear as soft bumps on or just under the skin, or grow more deeply along a nerve. Many people have a single neurofibroma with no underlying condition, but neurofibromas are also the hallmark tumor of neurofibromatosis type 1 (NF1), a genetic condition in which people develop many of them over a lifetime. A particular form called a plexiform neurofibroma grows in a tangled, rope-like way through and around a network of nerves; these are present from early in life in NF1, can become large, and may cause pain, disfigurement, or pressure on nearby structures. The reason neurofibromas matter medically is twofold. First, even though they are benign, large or plexiform tumors can press on nerves, the spine, the airway, or other organs and cause real symptoms. Second, in people with NF1 a plexiform neurofibroma carries a small but important lifetime risk of transforming into a cancer called a malignant peripheral nerve sheath tumor (MPNST) — so new pain, rapid growth, or a firming-up of a previously soft tumor is a warning sign that should be evaluated promptly. Most ordinary neurofibromas simply need observation. When treatment is needed, surgery has long been the main option, and a newer class of targeted medicines (MEK inhibitors) can shrink plexiform tumors that cannot be safely removed. Radiation has only a limited, carefully chosen role here, because in a genetic nerve-tumor syndrome it can raise the long-term risk of new tumors.

How radiation treats it.

Radiation therapy works by delivering focused energy that damages the DNA inside tumor cells so they can no longer grow and divide. For neurofibromas, the role of radiation is deliberately limited, and understanding why explains how it is used. Most neurofibromas are benign and either need no treatment or are best handled by surgery or, for plexiform tumors, a targeted oral medicine. On top of that, the majority of plexiform neurofibromas occur in people with neurofibromatosis type 1 (NF1), a genetic condition in which cells are already more prone to forming tumors; radiation to such tissue can raise the long-term risk of new tumors or of a benign tumor transforming into a cancer. For these reasons, radiation is not a routine treatment for benign neurofibromas and is reserved for carefully selected situations — for instance, a tumor near the spine or skull base that is causing problems and cannot be safely removed, where highly focused techniques such as stereotactic radiosurgery can control it while sparing nearby nerves and the spinal cord. Radiation takes on a much larger and more standard role if a neurofibroma transforms into a malignant peripheral nerve sheath tumor (MPNST). In that cancerous setting, radiation is used much as it is for other soft-tissue sarcomas: given before or after surgery to treat the microscopic disease that extends beyond the visible tumor and to reduce the chance the cancer comes back locally. Modern delivery — intensity-modulated radiation or proton therapy — concentrates the dose on the target and limits exposure to surrounding nerves and growing tissue, which matters most in younger patients and those with NF1. In short, for benign neurofibromas radiation is a niche tool used with caution, while for the cancer that can rarely arise from them it becomes a central part of curative treatment.

The ways we can treat it.

Stereotactic radiosurgery / focused radiation. Highly focused beams can control a benign nerve-sheath tumor that sits in a hard-to-reach spot, such as near the spine or skull base, when surgery would be too risky — used selectively because of the syndrome-related risk profile.

Adjuvant radiation for MPNST. When a neurofibroma has transformed into a cancer (MPNST), radiation before or after surgery treats microscopic disease around the tumor bed and lowers the chance of local recurrence, as it does for other soft-tissue sarcomas.

Intensity-modulated / proton radiation. Shaping the dose tightly around the target — or using proton beams — spares surrounding nerves, spinal cord, and developing tissue, which is especially important in younger patients and in NF1.

Questions we hear often.

Is a neurofibroma cancer? Almost always, no. The typical neurofibroma is benign — not cancer — and does not spread. Many cause no problems and simply need watching. The important exception is in people with NF1, where a plexiform neurofibroma carries a small lifetime risk of transforming into a cancer called MPNST, which is why new pain, rapid growth, or a tumor becoming hard should be checked promptly.

How are neurofibromas treated if they cause problems? Surgery is the main option for a symptomatic neurofibroma. For plexiform tumors in NF1 that cannot be safely removed, a targeted oral medicine (a MEK inhibitor) can shrink the tumor and ease symptoms. Radiation is used only in select situations, such as a tumor near the spine that can't be operated on, because in NF1 it can raise long-term tumor risk.

Why is radiation used so cautiously for neurofibromas? Most neurofibromas are benign and have good non-radiation options, and many occur in people with NF1, whose tissue is already prone to forming tumors. Radiation can increase the long-term risk of new tumors or of transformation in that setting, so it is reserved for carefully chosen cases. If a neurofibroma becomes a cancer (MPNST), radiation then plays a standard and important role alongside surgery.

This guide is informational only. It is not medical advice — please confirm anything here with your care team.