Skip to content
Inciteful Med

NF1 Tumors and Understanding Malignancy Risks

Last updated:

While most tumors in Neurofibromatosis Type 1 (NF1) are benign, individuals face an increased risk for certain cancers, including MPNST and breast cancer. Immediate medical evaluation is required if an existing tumor grows rapidly, becomes hard, or causes new or worsening pain.

Key Takeaways

  • • Cutaneous neurofibromas are benign skin bumps that do not turn into cancer, though they can cause physical and emotional distress.
  • • Plexiform neurofibromas grow along deep nerves and carry an 8% to 13% lifetime risk of transforming into a malignant cancer called MPNST.
  • • Red flags for tumor malignancy include rapid growth, new or worsening pain, texture changes, and new weakness or numbness.
  • • Children with NF1 require regular eye exams to monitor for optic pathway gliomas, which can affect vision or cause early puberty.
  • • Women with NF1 face a higher risk of breast cancer and should begin annual screening with a breast MRI and mammogram at age 30.

While most tumors associated with Neurofibromatosis Type 1 (NF1) are benign (non-cancerous), the condition does increase the risk for certain types of tumors and, in rarer cases, malignancies [1]. Understanding the different types of growths and knowing the “red flags” can help you monitor your or your child’s health with confidence.

Common Benign Tumors in NF1

The two most common types of tumors in NF1 are both benign, but they behave very differently.

1. Cutaneous Neurofibromas (cNFs)

These are small, pea-sized bumps that grow on or just under the surface of the skin [2].

  • When they appear: They usually start to appear during puberty and can increase in number throughout adulthood [3][4].
  • Risk and Impact: They are almost always benign and do not turn into cancer [5]. However, the primary concern goes beyond physical discomfort (they can be itchy or sensitive); developing multiple visible tumors can exact a severe psychological toll and heavily impact body image, leading to anxiety and emotional distress [6][3].

2. Plexiform Neurofibromas (pNFs)

These are more complex tumors that grow along large nerves deep within the body [6]. Doctors sometimes describe their texture as a “bag of worms” [7].

  • When they appear: pNFs are often present at birth or develop in early childhood [4].
  • Impact: Because they can grow large and involve multiple nerve branches, they may press on internal organs or affect movement or appearance [6].
  • Treatment: Complete surgical removal is often difficult because they are woven into healthy nerves [8]. However, newer medications called MEK inhibitors (like selumetinib) can help shrink these tumors in some patients [9].

Malignancy Risk: The MPNST

The most serious tumor complication in NF1 is the Malignant Peripheral Nerve Sheath Tumor (MPNST). This is a fast-growing cancer that usually develops from a pre-existing plexiform neurofibroma [5][10].

The lifetime risk of developing an MPNST for someone with NF1 is approximately 8% to 13% [11]. While this risk is relatively low, knowing the warning signs is critical for early detection.

Red Flags for Malignant Transformation

If you or your child has a known plexiform neurofibroma, contact your doctor immediately if you notice:

  • New or worsening pain: Persistent pain that wakes you up at night or isn’t related to an injury [12].
  • Rapid growth: A tumor that suddenly gets much larger over a few weeks or months [13].
  • Texture change: A soft tumor that becomes hard or firm to the touch [14].
  • Loss of function: New weakness, numbness, or tingling in a limb [12].

Other NF1-Related Tumors

Optic Pathway Gliomas (OPGs)

OPGs are benign tumors that grow on the nerves connecting the eye to the brain, occurring in about 15–20% of children with NF1 [15]. Most are found before age 7 [16]. While many stay small and never cause problems, some can affect vision or cause precocious puberty (early onset of puberty) [15][17]. Regular eye exams are the best way to monitor for these [18].

Adult Risks: Breast Cancer and GIST

As patients with NF1 grow into adulthood, they face higher risks for a few specific cancers compared to the general population:

  • Breast Cancer: Women with NF1 have a significantly higher risk of breast cancer, particularly before age 50 [19]. Early screening is frequently recommended starting at age 30, which typically includes an annual breast MRI in addition to a mammogram [19].
  • Gastrointestinal Stromal Tumors (GIST): These are rare tumors of the digestive tract that occur in about 5–7% of people with NF1 [20]. Symptoms to watch for include unexplained abdominal pain or anemia [21].
Tumor Type Typical Age Cancer Risk Key Monitoring
Cutaneous Neurofibroma Puberty+ Virtually zero Emotional support/Skin checks
Plexiform Neurofibroma Infancy+ 8–13% lifetime Watch for pain/rapid growth
Optic Pathway Glioma 0–7 years Benign Regular eye exams
Breast Cancer Adulthood Elevated Early screening (age 30+ MRI & Mammogram)
GIST Adulthood Potential Watch for abdominal symptoms

Frequently Asked Questions

Can the skin bumps from NF1 turn into cancer?
Cutaneous neurofibromas, the small bumps on the skin common in NF1, are almost always benign and do not turn into cancer. However, they can cause significant physical discomfort and emotional distress.
What is a plexiform neurofibroma?
A plexiform neurofibroma is a complex, benign tumor that grows along large nerves deep within the body and is often present at birth. While usually non-cancerous, they can sometimes transform into a fast-growing cancer called an MPNST.
What are the warning signs that an NF1 tumor might be cancerous?
Red flags for malignancy include a tumor growing rapidly over a few weeks or months, becoming hard or firm to the touch, causing new or persistent pain, or leading to new weakness or numbness in a limb. Contact your doctor immediately if you notice these changes.
How are optic pathway gliomas monitored in children with NF1?
Optic pathway gliomas are tumors on the nerves connecting the eye to the brain, most often found in children under seven. They are monitored through regular, specialized eye exams to check for vision changes or signs of early puberty.
Do people with NF1 have a higher risk of breast cancer?
Yes, women with NF1 have a significantly higher risk of developing breast cancer, especially before age 50. Doctors typically recommend early screening starting at age 30, which usually includes an annual breast MRI in addition to a standard mammogram.

Questions for Your Doctor

  • • Do I or my child have any plexiform neurofibromas, and if so, where exactly are they located?
  • • What specific changes in my or my child's skin bumps or deep tumors should I be looking for that would require an immediate visit?
  • • How often should I or my child have a specialized eye exam to check for optic pathway gliomas (OPGs)?
  • • At what age should I start screening for adult-related risks like breast cancer, and will standard mammograms be enough or do I need an MRI?
  • • Are there any clinical trials or newer treatments that I or my child might be a candidate for if the tumors grow?

Questions for You

  • • Have you noticed any of the bumps becoming firmer, growing quickly, or causing new pain?
  • • Do you ever experience vision changes, or have you noticed one eye appearing to bulge more than the other?
  • • Have you noticed any signs of early puberty in your child, such as unexpected growth spurts or physical changes?
  • • Are you keeping a log or photos of the skin spots and bumps to help track changes over time?

Want personalized information?

Type your question below to get evidence-based answers tailored to your situation.

References

  1. 1

    Neurofibromatosis -1 diagnosed from an intraoral swelling - a case series.

    Fahy E, Mulvihill C, O'Donoghue G, et al.

    Australian dental journal 2021; (66(2)):205-211 doi:10.1111/adj.12797.

    PMID: 32990942
  2. 2

    Cutaneous neurofibromas in the genomics era: current understanding and open questions.

    Allaway RJ, Gosline SJC, La Rosa S, et al.

    British journal of cancer 2018; (118(12)):1539-1548 doi:10.1038/s41416-018-0073-2.

    PMID: 29695767
  3. 3

    Integrative Analysis Identifies Candidate Tumor Microenvironment and Intracellular Signaling Pathways that Define Tumor Heterogeneity in NF1.

    Banerjee J, Allaway RJ, Taroni JN, et al.

    Genes 2020; (11(2)) doi:10.3390/genes11020226.

    PMID: 32098059
  4. 4

    The NF1 microdeletion syndrome: early genetic diagnosis facilitates the management of a clinically defined disease.

    Kehrer-Sawatzki H, Bäzner U, Krämer J, et al.

    Journal der Deutschen Dermatologischen Gesellschaft = Journal of the German Society of Dermatology : JDDG 2022; (20(3)):273-277 doi:10.1111/ddg.14707.

    PMID: 35246941
  5. 5

    Diagnostic and follow-up protocol for adult patients with neurofibromatosis type 1 in a Spanish reference unit.

    Solares I, Vinal D, Morales-Conejo M

    Revista clinica espanola 2022; (222(8)):486-495 doi:10.1016/j.rceng.2022.02.007.

    PMID: 35688675
  6. 6

    [Expert consensus on diagnosis and management of neurofibromatosis type 1 (2021 edition)].

    National Multi-Center Treatment Collaboration Group For Neurofibromatosis Type , National Multi-Center Research Platform For Plastic And Reconstructive Surgery

    Zhongguo xiu fu chong jian wai ke za zhi = Zhongguo xiufu chongjian waike zazhi = Chinese journal of reparative and reconstructive surgery 2021; (35(11)):1384-1395 doi:10.7507/1002-1892.202108065.

    PMID: 34779163
  7. 7

    Congenital cutaneous neurofibromas in neurofibromatosis type 1: Clinicopathological features in early infancy.

    García-Martínez FJ, Azorín D, Duat-Rodríguez A, Hernández-Martín Á

    Journal der Deutschen Dermatologischen Gesellschaft = Journal of the German Society of Dermatology : JDDG 2021; (19(1)):73-80 doi:10.1111/ddg.14322.

    PMID: 33448128
  8. 8

    Current concepts of neurofibromatosis type 1: pathophysiology and treatment.

    Choi J, An S, Lim SY

    Archives of craniofacial surgery 2022; (23(1)):6-16 doi:10.7181/acfs.2022.00633.

    PMID: 35255591
  9. 9

    Targeted Therapies in Neurofibromatosis Type 1.

    Sato AA, Earl D, Wallace SE

    American journal of medical genetics. Part C, Seminars in medical genetics 2025; (199(3)):154-160 doi:10.1002/ajmg.c.32151.

    PMID: 40968507
  10. 10

    Image-Based Differentiation of Benign and Malignant Peripheral Nerve Sheath Tumors in Neurofibromatosis Type 1.

    Liu J, Huang JN, Wang MH, et al.

    Frontiers in oncology 2022; (12()):898971 doi:10.3389/fonc.2022.898971.

    PMID: 35677169
  11. 11

    Imaging findings of type I neurofibromatosis with outcome of malignant peripheral nerve sheath tumor in the right lower extremity.

    Liu WH, Yang L, Wang XY, et al.

    Journal of clinical ultrasound : JCU 2024; (52(9)):1450-1452 doi:10.1002/jcu.23807.

    PMID: 39198889
  12. 12

    Spontaneous Hip Dislocation Complicating the Management of Malignant Peripheral Nerve Sheath Tumor Arising Within a Plexiform Neurofibroma.

    Mrowczynski OD, Vasekar M, Fox E, et al.

    Cureus 2021; (13(7)):e16320 doi:10.7759/cureus.16320.

    PMID: 34395108
  13. 13

    Malignant Peripheral Nerve Sheath Tumor Presenting as Horner's Syndrome.

    Azharudeen M, Selvaraj J, Pillai V, et al.

    Cureus 2021; (13(9)):e18341 doi:10.7759/cureus.18341.

    PMID: 34722092
  14. 14

    Malignant Transformation of Plexiform Neurofibroma Due to Neglected Giant Soft Tissue Swelling of the Back: A Case Report.

    Bin Abdul Halim WMA, Bin Mat Hassan S, Bt Awang M, Abdullah MAH

    Cureus 2024; (16(7)):e63807 doi:10.7759/cureus.63807.

    PMID: 39099914
  15. 15

    Neurofibromatosis Type 1-Associated Optic Pathway Gliomas: Current Challenges and Future Prospects.

    Tang Y, Gutmann DH

    Cancer management and research 2023; (15()):667-681 doi:10.2147/CMAR.S362678.

    PMID: 37465080
  16. 16

    Optic pathway glioma and the sex association in neurofibromatosis type 1: a single-center study.

    Henning AM, Handrup MM, Kjeldsen SM, et al.

    Orphanet journal of rare diseases 2021; (16(1)):489 doi:10.1186/s13023-021-02121-8.

    PMID: 34809690
  17. 17

    Impact of Optic Pathway Gliomas on Puberty and Growth in Neurofibromatosis Type 1: A 20-Year Experience From a Tertiary Center.

    Haysom R, Chinoy A

    Journal of child neurology 2025; (40(10)):882-888 doi:10.1177/08830738251341591.

    PMID: 40420702
  18. 18

    Natural history of optic pathway gliomas in a cohort of unselected patients affected by Neurofibromatosis 1.

    Trevisson E, Cassina M, Opocher E, et al.

    Journal of neuro-oncology 2017; (134(2)):279-287 doi:10.1007/s11060-017-2517-6.

    PMID: 28577031
  19. 19

    Breast Cancer Screening Utilization and Outcomes in Women With Neurofibromatosis Type 1.

    Yan K, Gao Y, Heller SL

    Clinical breast cancer 2023; (23(4)):e200-e205 doi:10.1016/j.clbc.2023.02.005.

    PMID: 36863889
  20. 20

    GIST associated with von recklinghausen disease: Report of two cases and review of literature.

    Vargas Ávila AL, Jiménez Leyva A, Vargas Flores J, et al.

    Annals of medicine and surgery (2012) 2021; (62()):365-368 doi:10.1016/j.amsu.2021.01.033.

    PMID: 33552495
  21. 21

    A rare unifocal gastric gastrointestinal stromal tumor in a young NF1 patient: A case report.

    Gupta S, Ahuja S, Kalwaniya DS

    International journal of surgery case reports 2025; (129()):111126 doi:10.1016/j.ijscr.2025.111126.

    PMID: 40054407

This page provides educational information about NF1 tumors and cancer risks. It is not a substitute for professional medical advice, diagnosis, or screening recommendations from your healthcare team.

Stay up to date

Get notified when new research about Neurofibromatosis type 1 is published.

No spam. Unsubscribe anytime.