The short answer
Sarcoma often causes a painless lump that grows over weeks or months, or bone pain and swelling. A growing lump needs prompt evaluation, and bone or back pain with leg weakness needs emergency care.
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 or joint pain and swelling over the bone. Osteosarcoma is most common in teens and young adults.
Sarcomas in the abdomen can cause worsening belly pain, or blood in the stool or vomit.
Any new or growing lump should be checked by a doctor. Most lumps are not sarcoma, but they still need to be looked at.
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This page is for anyone worried about a lump or bone pain, and for people who care about them. It covers the signs of soft tissue and bone sarcoma, and when to get urgent or emergency care.
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 symptoms are more often caused by other problems. So a lump or pain can be easy to put off. 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. Still, any new or growing lump should be checked by a doctor.
A sarcoma in the abdomen can behave differently. Tumors there can cause blockages or bleeding in the stomach or bowels, or press on nerves, blood vessels or nearby organs. Signs can include worsening abdominal pain, blood in the stool or vomit, or black, tarry stools.
Bone sarcoma symptoms
Bone sarcomas, such as osteosarcoma and Ewing sarcoma, most often cause:
- Pain in a bone or joint.
- Swelling over a bone.
- Limping or trouble walking.
- A bone that breaks for no known reason.
The National Cancer Institute says osteosarcoma is most common in teens and young adults. These symptoms can have other causes, and a doctor is the only way to know.
When to seek care
See a doctor promptly for a new or growing lump. Do the same for bone or joint pain that has no clear cause.
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 pressure on the spinal cord. The American Cancer Society calls it an oncology emergency, and untreated it can lead to paralysis.
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 bone that breaks for no known reason can be a sign of a bone tumor. Get urgent care right away.
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.
Common questions
What does a sarcoma lump feel like?
The American Cancer Society says most people with soft tissue sarcoma notice a lump that has grown over a few weeks or months. About half start in an arm or leg. The lump may or may not hurt. The American Cancer Society says these symptoms are more often caused by other things, but any new or growing lump should still be checked by a doctor.
How is bone sarcoma pain different from a normal ache?
The National Cancer Institute lists pain in a bone or joint, swelling over a bone, limping, and a bone that breaks for no known reason. These symptoms may be caused by osteosarcoma or by other problems. The only way to know is to see a doctor. Osteosarcoma is most common in teens and young adults.
Why are sarcomas often found late?
Sarcomas are rare. The American Cancer Society notes that their symptoms are more often caused by other things. A lump can be painless, which makes it easy to put off checking.
What symptoms need urgent attention?
See a doctor promptly for a new or growing lump, for bone or joint pain that is not explained, or for worsening abdominal pain. Blood in the stool or vomit, or black, tarry stools, can mean bleeding and needs urgent care.
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. The American Cancer Society calls this combination, which can mean pressure on the spinal cord, an oncology emergency. Untreated, it can lead to paralysis.
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Last updated: 2026-10-02Next 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, and this 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 then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. 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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