The short answer
Sarcoma often causes a painless lump that grows over weeks or months, or bone pain and swelling. Because early symptoms look like common injuries, sarcoma is often diagnosed later than other cancers. Some symptoms, like a growing lump over 5 centimeters or bone pain with leg weakness, need prompt or emergency evaluation.
A soft tissue sarcoma often shows up as a painless lump that keeps growing over weeks or months, most commonly in an arm or leg.
A bone sarcoma often causes bone pain and swelling that can be mistaken for a sports injury or growing pains, especially in teens and young adults.
Sarcomas in the abdomen can grow quietly and cause vague symptoms like bloating or pain before they are found.
A lump larger than about 5 centimeters (roughly a golf ball), a lump that is growing, or one that is deep under the muscle should be checked promptly.
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The full explanation.
The simple version
Sarcoma is a group of cancers that start in bone or in soft tissues like fat, muscle, nerves, and blood vessels. Sarcomas are rare, and their early symptoms often look like a bruise, a strain, or growing pains. So they are sometimes not recognized right away. Knowing what to watch for, and what needs urgent or emergency care, can help.
Soft tissue sarcoma symptoms
The most common first sign is a lump that has grown over a few weeks or months. It is most often felt in an arm or leg. It may or may not be painful. Most lumps like this are not sarcoma. But a few features make one worth checking promptly:
- It is growing in size.
- It is larger than about 5 centimeters (roughly a golf ball).
- It feels deep, firm, or fixed in place rather than soft and movable.
- It has come back after being removed before.
A sarcoma in the abdomen can behave differently. There is room for a tumor to grow there, so it may not be felt or cause pain until it is fairly large. Signs can include abdominal pain that slowly worsens, or a feeling of fullness. If the tumor presses on the stomach or bowel, there may be blood in the stool or vomit, or dark, tarry stools.
Bone sarcoma symptoms
Bone sarcomas, such as osteosarcoma and Ewing sarcoma, most often cause:
- Bone or joint pain that gets worse over time, or wakes someone up at night.
- Swelling near the affected bone.
- Limping or reduced use of an arm or leg.
- A fracture that happens without a significant injury.
These symptoms are especially easy to mistake for a sports injury. Teens and young adults are the group most often affected, which is one reason diagnosis can take longer than it should.
When to seek care
See a doctor promptly for a growing, large, or deep lump. Do the same for bone pain that is worsening or interfering with sleep.
Get emergency care right away — call 911 or go to the nearest emergency department — for back or bone pain along with new leg weakness, numbness, or loss of control of urine or stool. That combination can mean a tumor is pressing on the spinal cord. It is a medical emergency and needs fast treatment to prevent lasting nerve damage.
Go to an emergency department as well if a bone breaks after a small knock or with no injury at all, or if a limb suddenly buckles, looks bent, or cannot take your weight. A tumour can weaken bone from the inside, and a break like that needs imaging and orthopedic care the same day.
Sources
- National Cancer Institute, Soft Tissue Sarcoma Treatment (PDQ) – Patient Version, accessed August 3, 2026.
- National Cancer Institute, Osteosarcoma and Undifferentiated Pleomorphic Sarcoma of Bone Treatment (PDQ) – Patient Version, accessed August 3, 2026.
- American Cancer Society, Signs and Symptoms of Soft Tissue Sarcoma, accessed August 3, 2026.
- American Cancer Society, Bone Metastases, accessed August 3, 2026.
Words to know
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Common questions
What does a sarcoma lump feel like?
Most soft tissue sarcomas are first noticed as a lump that has grown over a few weeks or months, and about half start in an arm or leg. The lump may or may not hurt. Many lumps like this turn out to be harmless, but any lump that is growing, feels deep or firm, or is larger than about 5 centimeters (roughly the size of a golf ball) should be checked by a doctor.
How is bone sarcoma pain different from a normal ache?
Bone sarcoma pain often gets worse over time, can wake a person up at night, and does not go away with rest the way a typical strain or bruise would. It may be mistaken for a sports injury or growing pains at first, especially in teens and young adults, which is one reason diagnosis can be delayed.
Why are sarcomas often found late?
Sarcomas are rare, and their early symptoms — a painless lump, mild aching, or vague abdominal discomfort — overlap with far more common, harmless conditions. Abdominal sarcomas in particular can grow for a while before causing noticeable symptoms, since there is room in the abdomen for a tumor to expand.
What symptoms need urgent attention?
See a doctor promptly for a lump that is growing, larger than about 5 centimeters, or deep under the muscle; for bone pain that is worsening or wakes you at night; or for abdominal pain along with blood in the stool or vomit, which can suggest bleeding.
What symptoms are a medical emergency?
Back or bone pain along with new leg weakness, numbness, or loss of control of urine or stool needs emergency care right away. This combination can mean a tumor is pressing on the spinal cord, which can cause permanent damage if not treated quickly.
Questions to ask your doctor
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Plain-language explanation of the published sources cited on this page. AI-assisted, source-checked, not clinician-reviewed.
Last updated: 2026-08-18Next planned review: 2027-08-03
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and checked line by line against the sources listed on it. That confirms the sources support what the page says. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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Related articles
- Sarcoma: A Plain-Language Overview
- Types of Sarcoma: Bone and Soft Tissue Subtypes
- Sarcoma Stages: How Bone and Soft Tissue Sarcoma Are Staged
- Soft Tissue Sarcoma: A Plain-Language Overview
- Osteosarcoma: Symptoms, Stages, and Treatment
- Ewing Sarcoma: Symptoms, Stages, and Treatment
- Carcinoma vs. Sarcoma: What's the Difference?
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