FAP, Gardner Syndrome & Desmoid Tumours

What Are FAP and Gardner Syndrome — and Where Do Desmoids Fit In?

Familial adenomatous polyposis (FAP) is an inherited condition in which hundreds — sometimes thousands — of small growths called polyps develop in the lining of the large bowel, usually beginning in the teens or twenties. It is caused by a change (a "pathogenic variant") in a single gene called APC. Because the gene change can be passed from parent to child, FAP tends to run in families, and each child of an affected parent has roughly a 1-in-2 chance of inheriting it.

Gardner syndrome is not a separate disease — it is the name historically given to FAP when it shows up alongside features outside the bowel: bony lumps on the jaw or skull (osteomas), small skin cysts (epidermoid cysts), extra or unerupted teeth, and — importantly for this page — desmoid tumours. In modern practice, Gardner syndrome and FAP are understood as the same underlying APC condition along a spectrum, so a person described as having "Gardner syndrome" is, genetically, a person with FAP.

A desmoid tumour (also called desmoid-type fibromatosis or aggressive fibromatosis) is a growth of fibrous, scar-like cells. The word "aggressive" frightens people, but it describes only the local behaviour — desmoids can push into and stick to nearby tissue, yet they do not spread to the lungs, liver, or lymph nodes the way a true cancer does. You can read the full clinical picture of this tumour type on our dedicated page on the desmoid tumour (aggressive fibromatosis), and see how it sits among all soft tissue tumours on the sarcoma — overview hub.

Why Does FAP Raise the Risk of a Desmoid Tumour?

The answer lies in what the APC gene normally does. APC acts as a "brake" inside a cell-signalling pathway (the Wnt / beta-catenin pathway) that controls how often fibrous and lining cells divide. When the APC brake is faulty, that pathway stays switched on for too long — and the same loss of control that produces a carpet of bowel polyps can also drive fibrous cells to form a desmoid. So one inherited gene change produces two seemingly unrelated problems: too many polyps in the bowel, and an increased tendency to grow desmoids.

This is why desmoids in FAP have a recognisable pattern. They favour the abdomen, the mesentery (the sheet of tissue that holds the bowel) and the abdominal wall, far more often than the arms or legs where sporadic desmoids tend to appear. They also have a striking link to surgery and trauma: many FAP-associated desmoids appear in the months or few years after an abdominal operation — often the very colectomy performed to manage the polyps. Pregnancy and the hormonal changes around it can also act as a trigger in susceptible people.

Knowing this pattern changes how a careful team plans care. It is one of the reasons the timing and type of any abdominal surgery in someone with FAP is discussed thoughtfully — and why a new firm lump in the abdominal wall after such surgery is taken seriously rather than dismissed as scar tissue.

Who in the Family Should Consider Genetic Testing?

If you are reading this because a relative has FAP, Gardner syndrome, or an APC-related desmoid, the most useful single step is usually a conversation about genetic testing rather than years of quiet worry. Testing looks for the specific APC change in your family. A clear result is powerful: it tells each relative whether they carry the variant, and therefore whether they need lifelong bowel screening — or whether they can be reassured and step out of intensive surveillance altogether.

Genetic testing is usually discussed when one or more of the following apply:

• A parent, sibling, or child has a confirmed APC change or a diagnosis of FAP / Gardner syndrome.
• You or a relative has been found to have many bowel polyps at colonoscopy.
• A desmoid tumour has been diagnosed, especially in the abdomen or abdominal wall and at a young age.
• There are extra-bowel clues — jaw osteomas, multiple skin cysts, or dental abnormalities — that suggest Gardner syndrome.

Testing is best done with counselling, not in isolation — which is why our process starts with a sit-down to map your family tree, explain what each possible result means, and decide who should be tested first. The general principle is to test an affected relative first (so the family's specific variant is identified) and then offer simpler, targeted testing to everyone else. We walk through the practical detail on our companion page about genetic testing for sarcoma.

How a FAP-Associated Desmoid Is Diagnosed and Managed

When a person with FAP develops a firm, deep lump — most often in the abdominal wall or inside the abdomen — the first job is to confirm what it is, and the second is to decide whether it even needs treating. Both steps are deliberately unhurried, because rushing into surgery is rarely the right move with a desmoid.

Step 1 — Imaging and Biopsy to Confirm

An MRI (for abdominal-wall and limb desmoids) or a CT scan (for tumours deep inside the abdomen and mesentery) shows the size of the growth and its relationship to bowel, blood vessels, and the ureters. Where the diagnosis is not certain, a core needle biopsy confirms it is a desmoid and not a true sarcoma. In someone with known FAP and a typical abdominal desmoid, the picture is often clear enough that a careful team can avoid unnecessary procedures.

Step 2 — Active Surveillance First, in Many Cases

One of the most counter-intuitive facts about desmoids is that the modern, internationally-endorsed first step for many of them is active surveillance — careful watching with repeat scans rather than immediate treatment. Desmoids are unpredictable: a meaningful proportion stay stable, and some even shrink on their own. Because surgery for an FAP desmoid can itself trigger new desmoid growth, "watch carefully and treat only if it grows or causes symptoms" is often safer than operating straight away.

Step 3 — Systemic Therapy When Treatment Is Needed

If a desmoid is growing, causing pain, or threatening a vital structure such as the bowel, ureter, or a major vessel, treatment usually begins with medicines rather than the knife. Options used in step-up fashion include anti-inflammatory drugs (NSAIDs), anti-oestrogen (hormonal) tablets, newer targeted therapies that block the same Wnt pathway the desmoid relies on, and — for fast-growing or symptom-heavy tumours — low-intensity chemotherapy. Many desmoids are brought under control this way without any operation.

Step 4 — Surgery, Used Selectively

Surgery still has a role — for example, an abdominal-wall desmoid that can be removed cleanly, or a tumour that has not responded to other treatment. But in FAP it is chosen carefully, because operating in an abdomen that is prone to desmoids carries a real risk of provoking new ones. This is exactly the kind of trade-off a multidisciplinary tumour board exists to weigh.

Living With FAP: Screening, Family Planning, and Peace of Mind

For someone who carries an APC change, the priority is usually not the desmoid at all — it is regular bowel screening, because the polyp burden of FAP is what most affects long-term health and is highly manageable when watched. Colonoscopy on a planned schedule, beginning in the teens or early twenties, lets a gastroenterologist track polyps and act before they become a problem. Many people also have periodic checks of the upper digestive tract. The desmoid risk is layered on top of this and is monitored clinically and, when indicated, with imaging.

Because FAP is inherited in an autosomal dominant pattern, the diagnosis ripples outward to the whole family — and that is where calm, structured genetic counselling earns its place. Once the family's specific APC variant is known, untested relatives can have a simple, targeted test, and those who do not carry it can usually step out of intensive screening, sparing years of unnecessary procedures and anxiety. For couples thinking ahead, counselling also covers the reproductive options that exist for known carriers — a conversation many find deeply reassuring simply because the unknowns finally have names.

What CION Offers Families in Hyderabad

Indicative Cost in Hyderabad

Costs are indicative and vary with the laboratory and the test chosen. A personalised estimate is provided after your CION consultation. EMI options and cashless support through major TPAs, Aarogyasri, CGHS, ECHS & ESI are available for eligible patients.

Why Families Choose CION for FAP, Gardner & Desmoid Care

An inherited diagnosis is as much about the family as the patient. Here is why families across Telangana trust CION to handle it with clarity and care.

Turn Worry Into a Clear Plan

An APC change in the family does not have to mean years of uncertainty. One honest conversation can replace fear with a screening schedule, a desmoid plan, and answers for the people you love.