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CION Cancer Clinics
The NF1 gene: what it does and why it matters | CION Cancer Clinics
The NF1 gene makes a protein that acts as a brake on cell growth. When one copy is faulty from birth, the result is neurofibromatosis type 1, a lifelong condition that shapes the skin and the nerves. Most of the growths it causes are harmless. A few carry a real cancer risk, which is why people with NF1 are reviewed regularly for life. This page explains what the gene does and why that matters. At CION Cancer Clinics, our oncologists explain what a gene result means for you and your family, and plan the checks that follow.
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Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed September 2026, next review due September 2027
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On this page
- What does the NF1 gene actually do?
- What an NF1 fault looks like in the body
- How does a fault in NF1 turn into a lump?
- The NF1 words you will meet, in plain language
- Which NF1 growths are common, and which carry cancer risk?
- What this page cannot tell you
- Four things families tell us about NF1
- Common questions about the NF1 gene
The short answer
What does the NF1 gene actually do?
The NF1 gene tells your cells how to make a protein called neurofibromin. Its job is to switch off a growth signal inside the cell once that signal has done its work. When the gene is faulty, the signal stays on for longer than it should, and some cells grow when they should rest.
A brake on cell growth
Think of the growth signal as an accelerator. Neurofibromin is part of the brake. Genes that work like this are called tumour suppressor genes, because a working copy helps stop growths from forming. NF1 matters most in the cells that wrap around nerves, in the pigment cells of the skin and in parts of the brain.
What a faulty copy causes
A person born with one faulty copy of NF1 has a condition called neurofibromatosis type 1. It usually shows first as flat brown patches on the skin in early childhood. Later come soft lumps on or under the skin, called neurofibromas. Most of these are harmless. A small number of growths linked to NF1 can become cancer, which is why the gene sits on this site.
NF1 is a lifelong condition, not a cancer diagnosis. Most people with it live full working lives.Where it shows
What an NF1 fault looks like in the body
The same fault can look very different from one person to the next, even inside one family.
Skin
Flat, coffee-coloured patches called café-au-lait spots, often present in the first years of life. Freckles in the armpits and groin usually follow.
Nerves
Soft lumps growing from small nerves in the skin. Some people also have a larger, deeper growth along a nerve, called a plexiform neurofibroma.
Usually looks like
- Few lumps in childhood
- More appearing through the teens and adult life
Eyes and brain
Tiny harmless spots on the coloured part of the eye. Some young children develop a slow-growing tumour on the nerve to the eye, which is why eye checks matter early.
Bones, learning and blood pressure
Curving of the spine or a long bone, learning and attention difficulties, and raised blood pressure are all more common. Each is checked for at regular reviews.
Not sure whether this applies to you?
Ask an oncologistFrom fault to growth
How does a fault in NF1 turn into a lump?
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You carry two copies of NF1
One came from each parent. One working copy is enough to keep most cells behaving normally.
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An inherited fault removes one copy from birth
Every cell in the body now has only one working brake. Nothing is wrong yet, and many cells stay that way for life.
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The second copy is lost in a single cell
During ordinary life, one nerve-wrapping cell can lose its remaining working copy. That cell now has no brake at all.
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That cell grows into a neurofibroma
The cell divides and forms a lump. It stays benign in the great majority of people, meaning it does not spread.
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Rarely, further changes make it a cancer
In a small minority, a deep growth picks up more faults and turns into a cancer of the nerve sheath. This is the change doctors watch for.
On your report
The NF1 words you will meet, in plain language
- Neurofibromin
- The protein the NF1 gene makes. It acts as a brake on cell growth.
- Neurofibroma
- A soft, usually harmless lump growing from a small nerve.
- Plexiform neurofibroma
- A larger growth that spreads along a nerve under the skin. It needs closer watching than a skin lump.
- MPNST
- Malignant peripheral nerve sheath tumour. The main cancer linked to NF1, usually arising inside a plexiform neurofibroma.
- De novo
- A fault that appeared for the first time in this person. Neither parent carries it.
- Mosaic
- The fault is in some cells only, so the condition may affect just one part of the body.
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Side by side
Which NF1 growths are common, and which carry cancer risk?
Common and usually harmless
Less common and watched closely
Café-au-lait spots and freckling
A tumour on the nerve to the eye in young children
Small lumps on or under the skin
A deep growth that becomes painful or grows fast
Harmless spots in the eye
Breast cancer at a younger age in women
Learning and attention differences
Rare tumours of the gut wall and adrenal gland
Being straight with you
What this page cannot tell you
It cannot tell you how NF1 will behave in you or your child. Two people with the same fault can have very different lives. A few specific changes in the gene are linked to a milder or a more severe pattern, but for most families the variant does not predict what will happen.
It cannot read your report
What your specific variant means is a question for the counsellor who ordered the test. Bring the report to them, or to a clinical geneticist, rather than searching for the variant name online.
Who this does not apply to
One or two café-au-lait spots are common in children without NF1, and most people with a stray brown patch do not need a test. An NF1 change found only in a tumour, on a test used to plan cancer treatment, is a different finding. It does not mean you were born with NF1. Those tumour tests are explained on our targeted therapy pages.
If a report mentions NF1 and you cannot tell whether it came from blood or from a tumour, ask. The answer changes everything that follows.Commonly believed
Four things families tell us about NF1
"Something I did in pregnancy caused this."
Nothing a parent did causes NF1. About half of people with it are the first in their family, because the fault arose by chance in an egg or sperm cell.
"Every lump will turn into cancer."
Most neurofibromas stay harmless for life. The worry is a specific change in a deep growth, such as new pain, fast growth or hardening, and that is what reviews look for.
"My child's NF1 will be exactly like mine."
The fault is the same, but how it shows is not. A mildly affected parent can have a more affected child, and the reverse is just as common.
"Cousin marriage in our family caused it."
NF1 needs only one faulty copy, from one parent. Marrying within the family does not make it more likely, although it does matter for some other inherited conditions.
Questions we are asked
Common questions about the NF1 gene
Is NF1 a type of cancer?
No. NF1 is a genetic condition that mainly causes harmless growths on nerves and changes in the skin. It does raise the chance of a few specific cancers, which is why people with NF1 are reviewed regularly for life. Most people with NF1 never develop cancer.
What is the chance of passing NF1 to a child?
If you have NF1 in every cell, each child has a one in two chance of inheriting it. This is the same for sons and daughters. If your NF1 is mosaic, meaning only some cells carry it, the chance is lower, but a child who inherits it will usually have it in every cell.
Can NF1 skip a generation?
No. Everyone who carries the fault shows some signs, although they can be very mild. A parent with only a few brown patches may never have been diagnosed. Examining both parents carefully often answers the question.
Does NF1 get worse with age?
Skin lumps usually increase in number through the teenage years and adult life, and they can grow during pregnancy. Deep growths tend to grow fastest in childhood. How much this affects daily life varies widely, which is why reviews are set for each person.
My tumour test showed an NF1 change. Do I have NF1?
Not necessarily. NF1 changes are often found inside tumours such as lung cancer or melanoma, in people who were not born with NF1. Only a blood or saliva test answers whether the change is inherited. Your oncologist will say whether that test is worth doing.
Can the faulty gene be treated?
The gene fault itself cannot be corrected or reversed. Treatment is aimed at specific problems as they arise. Tablets that act on the same growth signal are now used for some deep growths that cannot be removed safely by surgery.
Will NF1 affect my child's schooling?
Many children with NF1 have some learning or attention difficulty, often mild. Most attend ordinary school. An early assessment and a word with the school make a real difference, and it is better done before problems build up than after.
Who should we see about NF1 in Hyderabad?
A genetic counsellor or clinical geneticist is the right first stop, with a paediatrician or neurologist for ongoing care. Counselling can be given in Telugu. Call the CION helpline if you are not sure where to start, and we will point you to the right clinic.
Your Specialists
Meet CION's oncologists. Bring your family history or genetic report to them.
Our medical oncologists see people with a strong family history of cancer, arrange genetic counselling and testing where it fits, and plan the checks that follow.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
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Sources
- MedlinePlus Genetics — NF1 gene
- MedlinePlus Genetics — Neurofibromatosis type 1
- GeneReviews (NCBI Bookshelf) — Neurofibromatosis 1
- NHS — Neurofibromatosis type 1 (NF1)
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
NF1 positive: what happens nextThe first year after a result, step by stepSurveillance for NF1 carriersWhich checks happen, and how oftenTesting the family for NF1Who else in the family should be checkedNF1 diagnostic criteria and café-au-lait spotsWhen brown patches point to NF1, and when they do not
Talk to us
Has someone in your family been told they have NF1?
Tell us what the report or the doctor said, and we will help you find the right counsellor and the right clinic for ongoing care. One helpline serves every CION centre.