Found A Firm Lump On A Tendon? What A Tendon Xanthoma Is, How It Differs From Other Lumps, And The Two Main Conditions It Points To
A tendon xanthoma is a firm, usually painless lump of cholesterol-laden cells inside a tendon, most often the Achilles. It isn’t harmful in itself, but it usually points to an inherited cholesterol condition, most often familial hypercholesterolemia and occasionally cerebrotendinous xanthomatosis. Other tendon lumps can look similar, so a doctor’s check and a blood test come first.
A tendon xanthoma is a firm deposit of fat-filled immune cells within a tendon, typically the Achilles or the tendons on the back of the hand. It forms when LDL cholesterol enters the tendon and is taken up by macrophages. It most often signals familial hypercholesterolemia. Ultrasound and blood tests confirm it, and it’s managed by lowering cholesterol.
Key Takeaways
- A tendon xanthoma is a firm cholesterol deposit inside a tendon.
- The Achilles tendon is the most common site.
- Familial hypercholesterolemia is the usual cause; CTX is a rare one.
- Gout, rheumatoid nodules and tendon-sheath tumors can look similar.
- Ultrasound is the preferred imaging test, with a blood fat profile.
- Lowering cholesterol is the main approach; surgery is for painful lumps.
On This Page 14 sections
What Is A Tendon Xanthoma?
A tendon xanthoma is a firm, slowly growing deposit of cholesterol-laden immune cells inside a tendon. It’s most common in the Achilles tendon, and it usually signals an inherited lipid disorder rather than a problem with the tendon itself.
Xanthomas are local deposits of lipid in body tissues, and the tendinous type is a gradually progressive lesion of the Achilles tendon, elbows and the extensor tendons of the hands, strongly associated with familial hypercholesterolemia.[1] The Achilles tendon is the most common site, and while tendon xanthomas often accompany familial hypercholesterolemia, other conditions can cause them too.[4]
This page focuses on a single lump: what it is, what else it might be, and what to do next. For every location and cause in depth, see our full guide to tendon xanthomas, and for the plural term, tendon xanthomata.
How Does A Tendon Xanthoma Form?
LDL cholesterol from the blood enters the tendon, where it’s chemically altered (oxidized). Immune cells called macrophages take up the altered cholesterol and become foam cells, which build up into a firm lump over years.
A review of Achilles tendon xanthomas describes the process: LDL from the circulation enters the tendon, is oxidized to oxidized LDL, and macrophages in the tendon actively take it up, forming the xanthoma.[4] More generally, in people with raised blood fats, lipoproteins seep into the skin and tendons and macrophages become foam cells.[1]
Because it takes years of high LDL, tendon xanthomas usually appear from the second decade of life onward in people with a predisposing condition.[1] In rarer disorders the lipid is different: cholestanol in cerebrotendinous xanthomatosis and plant sterols in beta-sitosterolemia.[1] Our guide to xanthomatosis explains what happens when many xanthomas appear.
What Should You Do If You’ve Found A Lump On A Tendon?
Note where it is, how it feels and whether there are others, then see your doctor and ask for a fasting blood fat test. Don’t wait for it to grow, and don’t try to remove it yourself.
- Check where it is. The Achilles, the backs of the hands and fingers, elbows and knees are typical xanthoma sites.[1][2]
- Feel it gently. Tendon xanthomas are firm, smooth and move with the tendon, and the skin over them usually looks normal.
- Look for others. Check both ankles and both hands; xanthomas are often on both sides.
- Look at your eyelids. Xanthelasma, soft yellow eyelid plaques, can also appear in familial hypercholesterolemia.[2]
- Think about family. High cholesterol or early heart attacks in relatives make an inherited cause more likely.
- See your doctor. Ask for a fasting lipid profile and an examination of the lump.[1]
Does A Tendon Xanthoma Hurt Or Affect Movement?
Usually not. Most tendon xanthomas are painless and found by chance. They can become sore when shoes rub on an Achilles xanthoma, and large ones can make a tendon feel thick or stiff.
Tendon xanthomas grow slowly,[1] which is why many people don’t notice them until a doctor, partner or podiatrist feels a thickened Achilles tendon. Symptoms are most likely where there’s friction: Achilles xanthomas rubbed by footwear are the ones most often removed surgically.[1] In a case conference on multiple hand and foot lumps, xanthomas were weighed against conditions that do cause pain and inflammation, such as gout and tuberculous tenosynovitis.[5]
- Shoes rubbing on the back of the heel can make an Achilles xanthoma sore; softer heel counters help.
- Stiffness or thickening of the tendon is worth mentioning to your doctor.
- Sudden pain, redness or heat isn’t typical of a xanthoma and points to something else, such as gout or inflammation.
- Pain on walking or sport should be checked, as thickened tendons can also be strained.
Our guide to xanthoma of the Achilles tendon covers heel symptoms in more detail.
What Else Can A Tendon Lump Be?
Gouty tophi, rheumatoid nodules, giant cell tumors of the tendon sheath, tuberculous tenosynovitis and nerve tumors can all cause lumps on or near tendons. Blood tests, imaging and sometimes a biopsy tell them apart.
A clinical case conference on multiple lumps in the hands and feet listed gouty tophi, tendon xanthomas, rheumatoid nodules, neurofibromatosis, giant cell tumor of the tendon sheath and tuberculous tenosynovitis as the conditions to consider, and explained how each differs:[5]
- Gouty tophi. Uric acid crystal deposits, often uneven from side to side, with calcification; a biopsy shows urate crystals.[5]
- Rheumatoid nodules. Appear later in rheumatoid arthritis, over pressure points, with joint deformity and positive rheumatoid factor.[5]
- Giant cell tumor of the tendon sheath. Usually a single painless lump in the hand or wrist.[5]
- Tuberculous tenosynovitis. Progressive, doughy or fluid-feeling swelling of the tendon sheath.[5]
- Nerve tumors (neurofibromatosis). Rarely affect the hands and feet and usually appear earlier in life.[5]
Tendon xanthomas, by contrast, are linked with familial hypercholesterolemia, favor the Achilles and extensor tendons, and show foam cells and cholesterol clefts without crystals under the microscope.[5] Our guide to skin xanthomas covers the xanthomas that sit in the skin rather than the tendon.
Tendon Lumps Compared
| Lump | Typical Features | Key Test |
|---|---|---|
| Tendon xanthoma | Firm, smooth, in the Achilles or hand extensor tendons, often both sides | Lipid profile; ultrasound; foam cells on biopsy |
| Gouty tophus | Uneven distribution, calcification, joint flares | Urate crystals on biopsy |
| Rheumatoid nodule | Over pressure points, with joint deformity | Rheumatoid factor |
| Giant cell tumor of tendon sheath | Usually one painless lump in hand or wrist | Biopsy |
| Tuberculous tenosynovitis | Doughy, progressive sheath swelling | Biopsy |
Condition One: Is A Tendon Xanthoma A Sign Of Familial Hypercholesterolemia?
Usually. Familial hypercholesterolemia is an inherited condition that causes very high LDL cholesterol from birth, affects about 1 in 250 to 1 in 500 people, and leads to tendon xanthomas in about 75% of older adults who have it.
About 75% of older adults with familial hypercholesterolemia have tendon xanthomas.[1] The condition affects about 1 in 500 to 1 in 250 people and is inherited in a dominant pattern, so each child of an affected parent has a 50% chance of having it. Its signs include xanthelasma and tendon xanthomas on the Achilles tendons, elbows, hands, knees and feet.[2] A related inherited condition, familial defective apolipoprotein B100, is also linked with tendon xanthomas.[5]
Without management, about half of men with familial hypercholesterolemia have a coronary event by 50, and about 30% of women by 60. Statins are the first-line medicine.[2] That’s why a tendon xanthoma is worth taking seriously even though the lump itself is harmless.
Condition Two: What Is Cerebrotendinous Xanthomatosis?
A rare inherited condition in which the body can’t break down cholesterol properly, so cholestanol builds up in the tendons, brain and eyes. It can cause tendon xanthomas without very high blood cholesterol, so it’s easy to miss.
Cerebrotendinous xanthomatosis (CTX) is caused by changes in the CYP27A1 gene and is inherited in a recessive pattern. It typically causes diarrhea in infancy, cataracts in childhood in about three-quarters of people, tendon xanthomas in the teens to twenties, and neurological decline in adulthood. It’s managed with chenodeoxycholic acid, and early care appears to prevent symptoms.[3]
Tendon xanthomas in someone with normal or only mildly raised cholesterol, especially with early cataracts, long-standing diarrhea or problems with walking, balance or memory, are a reason to ask about CTX. Measuring cholestanol in the blood helps diagnose it.[1]
How Is A Tendon Xanthoma Confirmed?
By examination, ultrasound and blood tests. Ultrasound is the preferred imaging test in everyday practice; a fasting lipid profile looks for the cause; and a biopsy is used only if the diagnosis is uncertain.
- Examination. A physical exam can reveal Achilles tendon xanthomas.[4]
- Ultrasound. The preferred imaging method in everyday clinical practice;[4] xanthomas appear as areas that lack the tendon’s normal fibrous pattern.[5]
- MRI. Helps rule out other conditions and plan surgery.[1]
- Fasting blood tests. Triglycerides, total, LDL and HDL cholesterol, with glucose and HbA1c as indicated.[1]
- Specialist tests. Genetic testing for familial hypercholesterolemia, or cholestanol if CTX is suspected.[1][2]
- Biopsy, if needed. Shows foamy cells, cholesterol clefts and giant cells, with no crystals.[5]
Imaging is useful because a xanthoma can thicken a tendon before it forms an obvious lump. On MRI, tendon xanthomas typically show a speckled or net-like pattern on cross-sectional images,[5] and ultrasound can show the loss of the tendon’s normal fibrous structure.[5] Either can also reveal xanthomas in the other ankle or hand that you can’t yet feel, which helps your doctor judge how widespread the problem is.
How Is A Tendon Xanthoma Managed?
By managing the condition behind it. Statins come first for familial hypercholesterolemia, with PCSK9 inhibitors or LDL apheresis for some people. Lumps that hurt or rub can be removed surgically, combined with cholesterol control.
- Statins. The first-line medicine for familial hypercholesterolemia;[2] they lower blood fats and may shrink xanthomas.[1]
- PCSK9 inhibitors. Injectable medicines effective in familial hypercholesterolemia.[1]
- LDL apheresis. Filtering LDL from the blood, one of the approaches proposed for Achilles tendon xanthomas.[4]
- Chenodeoxycholic acid. The medicine used for CTX.[3]
- Surgery. For painful lumps or those rubbed by shoes, complete excision with medical control is preferred; partial removal tends to recur.[1]
Surgery on the Achilles needs particular care, because the area heals poorly.[1] Small xanthomas often shrink with control of the underlying disease.[1] Our guides to Achilles tendon xanthoma and xanthoma of the Achilles tendon cover the ankle in more detail.
Should Your Family Be Checked?
Yes. Familial hypercholesterolemia passes to half of an affected parent’s children, so parents, brothers, sisters and children should have their cholesterol tested. For CTX, brothers and sisters are the ones most at risk.
Because familial hypercholesterolemia is dominant, each child of an affected parent has a 50% chance of inheriting it.[2] CTX is recessive, so it tends to appear in siblings, and early care appears to prevent symptoms.[3] Testing relatives early can find people who need care before any lumps appear. Our guide on whether xanthelasma is genetic explains how these inherited conditions can show up on the eyelids as well.
What If You Were Looking For The Eyelid Type?
Then you’re probably thinking of xanthelasma: soft, flat yellow plaques near the inner corners of the eyelids. It’s a different kind of xanthoma, far more common, and often appears with normal cholesterol.
Xanthelasma and tendon xanthomas can occur together in familial hypercholesterolemia,[2] so if you have both, tell your doctor. On their own, eyelid plaques are much less strongly tied to an inherited disorder. Our main xanthelasma guide and what xanthelasma looks like cover the eyelid type, and our xanthomas guide covers every type side by side.
What’s The Bottom Line On Tendon Xanthoma?
A tendon xanthoma is a firm cholesterol deposit inside a tendon, most often the Achilles. It usually points to familial hypercholesterolemia, occasionally to cerebrotendinous xanthomatosis, and needs a doctor’s assessment, ultrasound and blood tests.
The lump itself is harmless, but the condition behind it can raise heart risk or, rarely, affect the nervous system, and both are very manageable once found. Lowering cholesterol can shrink the lumps, surgery helps painful ones, and testing your family can protect them too. For a quick definition, see xanthoma tendon or what is xanthoma; if you meant the eyelid plaques, see our main xanthelasma guide, and browse all our xanthelasma and xanthoma guides.
Common Questions About Tendon Xanthoma
What Is A Tendon Xanthoma?
It’s a firm, slowly growing deposit of cholesterol-laden immune cells inside a tendon, most often the Achilles tendon.
What Causes A Tendon Xanthoma?
LDL cholesterol enters the tendon, is oxidized and is taken up by macrophages, usually because of familial hypercholesterolemia.
What Conditions Does A Tendon Xanthoma Point To?
Most often familial hypercholesterolemia; less often cerebrotendinous xanthomatosis, which can occur without very high cholesterol.
How Do I Know If My Lump Is A Tendon Xanthoma?
Only a doctor can confirm it. Ultrasound and blood tests usually settle it, with a biopsy if gout, rheumatoid nodules or a tendon-sheath tumor need ruling out.
Is A Tendon Xanthoma Dangerous?
The lump is benign, but the condition behind it can raise the risk of early heart disease, so it needs checking.
Can A Tendon Xanthoma Shrink?
Yes, it can shrink once cholesterol is controlled. Painful lumps can be removed surgically alongside cholesterol control.
Which Doctor Should I See?
Start with your family doctor, who can arrange blood tests and refer you to a lipid clinic, or to a surgeon if the lump is troublesome.
Should My Family Be Tested?
Yes. Familial hypercholesterolemia passes to half of an affected parent’s children, and CTX tends to affect brothers and sisters.
Sources
- Bell A, Shreenath AP. Xanthoma. StatPearls, National Library of Medicine (NCBI Bookshelf), updated 2023.
- Ison HE, Clarke SL, Knowles JW. Familial Hypercholesterolemia. GeneReviews, National Library of Medicine (NCBI Bookshelf), revised 2025.
- Federico A, Gallus GN. Cerebrotendinous Xanthomatosis. GeneReviews, National Library of Medicine (NCBI Bookshelf), revised 2024.
- Tsouli SG, Kiortsis DN, Argyropoulou MI, Mikhailidis DP, Elisaf MS. Pathogenesis, detection and treatment of Achilles tendon xanthomas. European Journal of Clinical Investigation, 2005.
- Kapoor SK, Kataria H, Patra SR, Boruah T. Multiple Nodular Outgrowths in the Hands and Feet of a 60-year-old Man. Clinical Orthopaedics and Related Research, 2009;468(2).
