Medical Oncologist
CION Cancer Clinics
FLCN mutation: which cancers, and how much risk | CION Cancer Clinics
An FLCN fault mainly raises the risk of kidney cancer. Tumours are often in both kidneys and usually grow slowly, so regular scans can find them small. The lung cysts and skin bumps that come with the fault are not cancers. This page explains which organs are affected, why the risk is not a certainty, and what the published figures can and cannot tell you. 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
- Which cancer does an FLCN fault raise the risk of?
- What does the risk look like in each part of the body?
- Why does an FLCN fault not always lead to cancer?
- What do the words about FLCN risk mean?
- How is kidney cancer in BHD different?
- What can this page not tell you?
- What do families get wrong about FLCN and cancer?
- Common questions about FLCN cancer risk
The short answer
Which cancer does an FLCN fault raise the risk of?
The main cancer risk with an FLCN fault is kidney cancer. Carriers have a higher chance of kidney tumours than other people, often in both kidneys and often more than one. The fault also causes lung cysts and skin bumps, but neither of those is a cancer.
The condition behind the risk
An inherited FLCN fault causes Birt-Hogg-Dubé syndrome, usually called BHD. The kidney tumours in BHD tend to grow slowly. Many are found on a routine scan long before they cause pain or blood in the urine. Some are harmless growths and some are cancers, and a single kidney can hold both kinds.
How big is the risk?
It is raised, but most carriers never develop a kidney tumour. The published figures come from small groups of families, mostly in Europe, North America and Japan, and they differ from study to study. Your team will talk about risk in terms of which checks you need, not a single number. What is agreed is that regular kidney scans find tumours while they are small.
An FLCN fault raises risk. It is not a cancer diagnosis.Organ by organ
What does the risk look like in each part of the body?
The same fault behaves differently in different organs. Only one of them carries a clear cancer risk.
Kidneys
The one real cancer risk. Tumours are often in both kidneys and usually grow slowly. They are commonly found in middle age, though younger carriers are affected too.
Tumour types seen in BHD
- Chromophobe kidney cancer
- Mixed or hybrid tumours
- Oncocytoma, which is not a cancer
- Rarely, faster-growing types
Lungs
Most adult carriers have air-filled cysts in the lower lungs. These are not cancer and do not turn into cancer. Their risk is a collapsed lung, not a tumour.
Skin
Small, pale bumps on the face, nose and neck. They are harmless and do not become skin cancer. They are often the clue that leads a dermatologist to suspect BHD.
Bowel and thyroid
A few studies have looked for a link. The evidence is weak and conflicting, and it does not change routine care. Your team may still suggest a bowel check if a relative had bowel cancer.
Studies so far are small. This may change.Not sure whether this applies to you?
Ask an oncologistFrom fault to tumour
Why does an FLCN fault not always lead to cancer?
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Every cell starts with one working copy
A carrier is born with one faulty copy of FLCN and one working copy in every cell. The working copy keeps the cell's growth brake on.
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The working copy is lost in one kidney cell
Over many years, chance damage can knock out the second copy in a single cell. That cell now has no brake.
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A small, slow tumour forms
The cell starts to divide when it should not. In BHD this usually happens slowly, over years, and the tumour stays small for a long time.
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A scan finds it early
Regular scans pick up these tumours while they are small. Many are simply watched with repeat scans rather than removed straight away.
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Surgery saves as much kidney as possible
When a tumour does need treatment, surgeons remove only the tumour and keep the rest of the kidney. New tumours can form later, so the kidney tissue is precious.
On your report
What do the words about FLCN risk mean?
- Birt-Hogg-Dubé syndrome (BHD)
- The inherited condition caused by an FLCN fault. It brings skin bumps, lung cysts and a raised kidney tumour risk.
- Penetrance
- How often a fault actually leads to illness across everyone who carries it. For FLCN kidney tumours, it is well short of everyone.
- Chromophobe
- A type of kidney cancer that usually grows slowly. It is one of the types most often seen in BHD.
- Oncocytoma
- A kidney growth that is not a cancer. In BHD it can sit beside a cancer in the same kidney.
- Bilateral and multifocal
- Bilateral means in both kidneys. Multifocal means more than one tumour in the same kidney.
- Nephron-sparing surgery
- An operation that removes only the tumour and keeps the healthy part of the kidney working.
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Side by side
How is kidney cancer in BHD different?
Kidney tumours in BHD
Kidney cancer in most people
Often in both kidneys, often several
Usually one tumour in one kidney
Usually slow-growing types
Most often the clear cell type
Small tumours are often watched
Most tumours are treated when found
New tumours can appear years later
A second tumour is uncommon
Relatives can be tested
No family test is needed
Being straight with you
What can this page not tell you?
It cannot give you your own risk. What your specific variant means is a question for the counsellor who ordered the test. They will look at the exact change, your age, any scans you have had and who in the family has been affected.
It cannot say whether a tumour on your scan is a cancer
Scans show size and shape. They cannot always tell a harmless oncocytoma from a slow cancer. Your urologist and radiologist decide together whether to watch a tumour or remove it.
Who this does not apply to
Most people with kidney cancer do not carry an FLCN fault, and most do not need this test. If you have one kidney tumour found later in life, with no lung cysts, no collapsed lung and no skin bumps in the family, BHD is unlikely. Testing the tumour itself for treatment choices is a different question, covered on our targeted therapy pages.
Commonly believed
What do families get wrong about FLCN and cancer?
"The lung cysts will turn into lung cancer."
They do not. The cysts are thin air pockets, and their only real risk is a collapsed lung. BHD does not raise the risk of lung cancer.
"A kidney tumour means the kidney must come out."
In BHD, surgeons try hard to keep the kidney. Small tumours are often watched, and larger ones are removed on their own. This matters because new tumours can form later.
"No kidney cancer in the family means low risk."
Small families may simply not show it yet. The risk comes from carrying the fault, not from how many relatives were affected. Carriers are offered scans either way.
"Skin bumps mean the cancer has started."
The bumps are harmless. They point to the gene fault, which is why the kidneys then need checking, but they say nothing about whether a tumour is present.
Questions we are asked
Common questions about FLCN cancer risk
Will I definitely get kidney cancer?
No. Many carriers never develop a kidney tumour at all. The risk is raised compared with other people, which is why carriers are offered regular kidney scans. Those scans are there to find any tumour while it is small and simple to deal with.
At what age do kidney tumours usually appear?
Most are found in middle age, but younger adults can be affected. That is why scans usually start in early adult life rather than waiting. Your team will set the starting point based on your family history.
Are BHD kidney cancers aggressive?
Most are slow-growing types, and many are found before they spread. A small share are faster-growing, which is one reason scans are not skipped. Your urologist will explain what your own scan shows.
Does an FLCN fault raise the risk of other cancers?
Kidney cancer is the only clear link. Studies of bowel, thyroid and skin cancer have given mixed answers. If a relative had one of these, tell your counsellor, who may suggest extra checks for your family.
Is the risk the same for men and women?
The kidney risk seems broadly similar in men and women, and the fault passes to sons and daughters equally. Each child of a carrier has a one in two chance of inheriting it, whichever parent carries it.
Can I lower my risk?
You cannot remove the gene fault. You can stop smoking, keep your blood pressure and weight in check, and keep every scan appointment. Those steps protect the kidneys and help any tumour be found early.
Does this affect my children's marriage prospects?
Families often worry about this. BHD is a manageable condition with regular checks, and many carriers live full lives. When and how to share the result is a personal choice, and a counsellor can help you think it through in Telugu.
Where should I start if I have just been told?
Ask for a kidney scan plan, a genetic counselling appointment and a list of relatives who should be offered testing. Call the CION helpline if you are not sure who to see, 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
- GeneReviews (NCBI) — Birt-Hogg-Dubé Syndrome
- MedlinePlus Genetics — Birt-Hogg-Dubé syndrome
- National Cancer Institute — Genetics of Kidney Cancer (Renal Cell Cancer) (PDQ)
- MedlinePlus Genetics — FLCN gene
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
The FLCN gene: what it does and why it mattersStart here if BHD is new to youSurveillance for FLCN carriersWhich kidney scans carriers have, and when they startFLCN positive: what happens nextThe first few steps after a positive resultTesting the family for FLCNWhich relatives should be offered a test
Talk to us
Have you been told you carry an FLCN fault?
Tell us what the report says and who in the family has been affected. We will help you arrange a kidney scan plan and genetic counselling. One helpline serves every CION centre.