Do Cutaneous Neurofibromas Turn Into Cancer?

The short answer is no. The small, soft bumps on the surface of your skin—known medically as cutaneous neurofibromas—are benign (non-cancerous) and do not turn into cancer ^[1]. Because these skin tumors are highly visible and can grow in large numbers, it is incredibly common for people with Neurofibromatosis type 1 (NF1) to worry about them becoming dangerous. However, while they can be itchy, uncomfortable, or cosmetically distressing, cutaneous neurofibromas are strictly a surface-level skin issue and do not have a risk of malignant transformation ^[1].

While they will not turn into cancer, cutaneous neurofibromas can take a heavy emotional toll. If specific bumps are causing you physical discomfort or significant cosmetic anxiety, a dermatologist or NF specialist can often remove them through minor surgical procedures ^[2].

Understanding the Difference: Cutaneous vs. Plexiform

To understand your actual cancer risk in NF1, it is essential to know the strict difference between cutaneous neurofibromas and plexiform neurofibromas.

• Cutaneous Neurofibromas (cNF): These grow on or just beneath the surface of the skin. They move easily when you touch them, are usually soft, and, most importantly, they stay benign ^[1].
• Plexiform Neurofibromas (pNF): These tumors grow deeper inside the body and involve larger nerve branches ^[3]. They are often present at birth, though they might not be noticed until later. They can sometimes feel like a thick cord or a “bag of worms” under the skin, or they may be completely invisible from the outside and only found on scans ^[3].

Unlike the superficial skin bumps, plexiform neurofibromas do carry a risk of turning into cancer ^[4]. Research shows that people with NF1 have an 8% to 13% lifetime risk of a deep plexiform tumor transforming into an aggressive cancer known as a Malignant Peripheral Nerve Sheath Tumor (MPNST) ^[5].

While that statistic is frightening, it is important to know that not everyone with NF1 has a plexiform tumor (they occur in up to half of patients) ^[6]. If you are ever unsure whether a lump is just a harmless surface bump or a deeper plexiform tumor pushing up, ask your doctor to evaluate it.

What to Watch For

Because deep plexiform tumors can change, monitoring them is a critical part of your routine NF1 care. While you do not need to worry about your surface-level cutaneous bumps turning into cancer, you should be vigilant about deeper lumps.

Contact your doctor if you notice any of the following changes in a deeper tumor:

• Rapid growth: A tumor that suddenly gets noticeably larger ^[4].
• New or unmanageable pain: Pain that wakes you up at night, doesn’t go away, or feels different than your normal baseline ^[4].
• Change in texture: A lump that previously felt soft but suddenly becomes firm or hard ^[4].
• New weakness or numbness: Changes in how your muscles function or how you feel sensations in the area around a tumor ^[4].

Your care team can use advanced imaging, such as a Whole-Body MRI (WBMRI) or PET scans, to establish a baseline of any hidden internal tumors and evaluate suspicious changes ^[7][8]. This ensures that if a tumor does become malignant, it is caught as early as possible to provide the best treatment options ^[7].