Medical Oncologist
CION Cancer Clinics
Recognising when an NF1 lump has changed | CION Cancer Clinics
Most lumps in NF1 stay harmless for life. A small number, usually the deeper plexiform kind, can change into a cancer called a malignant peripheral nerve sheath tumour, and catching that change early gives the best chance of removing it completely. This page explains which changes matter, what to watch for at home, what tests follow, and which changes are usually nothing to worry about. At CION Cancer Clinics, our oncologists plan screening and care for families with an inherited cancer syndrome, explained in plain words.
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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
- When should an NF1 lump worry you?
- Which changes should be reported to your doctor?
- What tests follow when a lump has changed?
- The words you will meet, in plain language
- Which changes are usually harmless, and which are not?
- What this page cannot tell you
- Four things families believe about NF1 lumps
- Common questions about changing lumps in NF1
The short answer
When should an NF1 lump worry you?
When it changes in a way that is new for that lump. Pain that does not settle, fast growth, a lump turning hard, or new weakness or numbness nearby all need a doctor to look within days, not months. Most lumps in NF1 never do any of these things.
Why most lumps are not the concern
The small soft lumps on the skin, which often multiply after puberty, are almost never the problem. They can be a nuisance and affect how a person feels about their appearance, but they are not the lumps that turn cancerous.
Which lumps doctors watch more closely
The concern is mainly with plexiform neurofibromas. These are larger lumps that grow along a nerve and its branches, sometimes deep inside the body where they cannot be seen. In a minority of people with NF1, part of one of these can change into a cancer called a malignant peripheral nerve sheath tumour. The risk is far higher than in the general population, which is why changes are taken seriously.
A new symptom is a reason to be checked. It is not a diagnosis.What to watch for
Which changes should be reported to your doctor?
These are the changes specialists ask families to report. One of them alone is enough to book a review.
Pain that is new or will not settle
Pain in or around a lump that lasts, keeps coming back, or wakes the person at night. Ordinary painkillers stop working as well as they did.
Growth you can notice
A lump that is visibly bigger over a few weeks, or clothes and shoes that stop fitting because of it. Plexiform lumps can grow slowly in childhood, so it is a change in pace that matters.
A change in feel
A part of a lump that was soft becoming firm or hard, or feeling fixed to the tissue underneath when it used to move.
New nerve symptoms
Weakness, numbness or tingling in the arm or leg near the lump, or a new limp. For a lump near the spine, new trouble passing urine or controlling the bowels needs same-day care.
Higher-risk groups
- People with large or deep plexiform lumps
- Anyone who had radiotherapy in the past
- A previous biopsy showing an atypical lump
Not sure whether this applies to you?
Ask an oncologistAfter you report a change
What tests follow when a lump has changed?
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An examination and a history
The doctor asks when the change began and how fast it has moved, then examines the lump and checks strength and feeling in the limb. Bring any old photos or scans for comparison.
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An MRI scan
MRI shows the size and shape of the lump and whether any part looks different from the rest. It is compared with earlier scans where they exist.
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A PET-CT scan, in many cases
A PET-CT can show which part of a large lump is most active. That helps the team decide whether a biopsy is needed and exactly where to take it.
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A biopsy from the right spot
A needle sample is taken from the most active area. A change can sit in one small corner of a big lump, so aiming matters.
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A plan from a specialist team
If cancer is found, a team that treats sarcomas plans surgery, sometimes with radiotherapy or chemotherapy. If the lump is benign, you return to regular review.
On your report
The words you will meet, in plain language
- Cutaneous neurofibroma
- A small soft lump in or on the skin. It is the common lump of NF1 and is not expected to become cancerous.
- Plexiform neurofibroma
- A larger lump that spreads along a nerve and its branches, often present from early childhood.
- Atypical neurofibroma
- A lump whose cells look unusual under the microscope but are not cancer. It is often removed because it can progress.
- MPNST
- Short for malignant peripheral nerve sheath tumour. A cancer that can grow from a plexiform or atypical neurofibroma.
- PET-CT
- A scan that shows how active different areas of tissue are, which helps find the part of a lump that has changed.
- Sarcoma team
- Surgeons, oncologists and radiologists who specialise in cancers of soft tissue and nerves.
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Side by side
Which changes are usually harmless, and which are not?
Usually expected
Needs a doctor to look
More small skin lumps appearing after puberty or in pregnancy
One lump growing clearly faster than the rest
Mild itching or tenderness when a lump is knocked
Constant pain, or pain that wakes you at night
A plexiform lump growing slowly with the child
A sudden change in its pace of growth in adult life
A lump that stays soft and moves under the skin
A part that turns hard or fixed
Normal strength and feeling around the lump
New weakness, numbness or tingling nearby
Being straight with you
What this page cannot tell you
It cannot tell you whether a particular lump has changed. Only an examination and, usually, a scan can answer that. If you are worried about a lump right now, do not wait for your next routine appointment. Ask for an earlier one and say what has changed.
It cannot read a scan or a biopsy report
Reports on nerve lumps use careful, technical wording, and a single phrase can shift the plan. Ask the doctor who ordered the scan to take you through it. What your specific gene variant means is a question for the counsellor who ordered the genetic test.
Who this does not apply to
Most people with NF1 will never develop this cancer, and most of the lumps they live with will stay benign. This page is also not for lumps in people without NF1, which have a different set of causes. Studies on how best to watch plexiform lumps are still small, and practice varies between centres.
Keeping dated photos of visible lumps on your phone makes change much easier to spot and to show a doctor.Commonly believed
Four things families believe about NF1 lumps
"Every new lump means cancer is coming."
New skin lumps are an expected part of NF1, especially in the teens and in pregnancy. What matters is a change in one lump, not the arrival of more.
"Cutting a lump or taking a biopsy makes it spread."
A properly planned biopsy does not cause cancer or make it spread. Planning where and how it is taken matters, which is why it is best done by the team that would treat the lump.
"If it does not hurt, it cannot be serious."
Pain is a common early sign, but not the only one. Fast growth, hardening or new weakness count too, even without pain.
"Removing all the lumps early will stop cancer."
Deep plexiform lumps often cannot be removed fully without harming the nerve. Watching closely and acting on change is usually safer than operating on every lump.
Questions we are asked
Common questions about changing lumps in NF1
How quickly should a changed lump be seen?
Within days rather than weeks for persistent pain, fast growth or hardening. The same day if a lump near the spine comes with new weakness in the legs, or new trouble passing urine or controlling the bowels. Earlier is always better than waiting to be sure.
Can the small skin lumps turn into cancer?
They are not expected to. The cancer linked to NF1 grows from the deeper plexiform or atypical lumps. Skin lumps can still be removed for comfort or appearance, and any lump that behaves differently from the others should be checked.
Does everyone with NF1 need regular body scans?
Not every centre does routine whole-body scans. Some offer a whole-body MRI in late teens or early adult life to map deep plexiform lumps. Your team will say whether that suits you, and will always scan when symptoms change.
Is there a medicine that shrinks plexiform lumps?
A tablet called selumetinib can shrink some plexiform neurofibromas that cannot be removed safely. It is a specialist decision with regular monitoring. It does not replace checking a lump that has changed, and it is not a treatment for cancer.
What if the biopsy shows an atypical neurofibroma?
It means the cells look unusual but are not cancer. Many teams advise removing it where that can be done safely, because it can progress over time. It also means closer follow-up for that area afterwards.
Can children with NF1 get this cancer?
It can happen in teenagers, but it is more often found in adults. Children with plexiform lumps are watched in regular reviews, and parents are taught which changes to report. A child's complaint of lasting pain in a lump should be taken seriously.
Does NF1 raise the risk of other cancers?
Yes, for a few. Women with NF1 have a raised breast cancer risk and usually start screening younger. There are also rarer tumours of the brain, gut and adrenal gland. Your NF1 team will explain which checks apply to you.
Who should we see about a changing lump?
Start with the doctor who follows the NF1, and ask for a scan to be arranged promptly. If cancer is a possibility, the lump should be managed by a team experienced in sarcomas. Call the CION helpline and we will help you reach the right specialists.
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)
Medical Oncologist
Medical Oncologist
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Sources
- GeneReviews (NCBI Bookshelf) — Neurofibromatosis 1
- NHS — Neurofibromatosis type 1
- MedlinePlus Genetics — Neurofibromatosis type 1
- American Academy of Pediatrics (Pediatrics) — Health Supervision for Children With Neurofibromatosis Type 1
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 surveillance through childhoodThe routine checks that catch changes earlyLiving with visible skin changesCoping with the lumps that are harmless but still hardNF1, NF2 and schwannomatosis: three different conditionsMake sure the right condition is on the reportLearning and development in NF1The other side of NF1 that families often ask about
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