ConditionCancer
Soft Tissue Sarcoma
Soft tissue sarcoma is a rare cancer that starts in the body's connective tissues: fat, muscle, nerves, blood vessels, fibrous tissue and the tissue around joints. There are more than 50 subtypes. Most appear as a painless lump in an arm or leg, though they can arise in the abdomen, chest or head and neck. A lump larger than 5 cm (2 inches), deep under the muscle layer, or growing should be checked with imaging. Treatment centers on surgery, often with radiation, at a specialist sarcoma center.
Also called: Sarcoma, connective tissue cancer, STS, liposarcoma, leiomyosarcoma and other subtypes
At a glance
- What it is
- Cancer arising in connective tissues such as fat, muscle, nerves and vessels.
- How common
- Rare; about 13,000 new cases a year in the US, under 1% of adult cancers.
- Where
- Arms and legs (about 60%), trunk, abdomen (retroperitoneum), head and neck.
- Warning signs
- A growing lump, larger than 5 cm, deep, or painful; abdominal swelling.
- Diagnosis
- MRI or CT, then core needle biopsy at a sarcoma center.
- Treatment
- Surgery, radiation, and sometimes chemotherapy or targeted therapy.
When to get help
See a doctor within a day or two
- A lump that is growing, larger than about 5 cm (2 inches), firm, deep under the skin or muscle, or painful: ask for an ultrasound or MRI promptly
- A lump that comes back after being removed
- Abdominal swelling, fullness or pain with weight loss
Book a routine appointment
- Any new lump lasting more than 4 weeks
- A soft, small, slow-growing lump under the skin that has not changed, for review
- People with Li-Fraumeni syndrome, neurofibromatosis type 1 or past radiation: report new lumps
What soft tissue sarcoma is
Sarcomas develop from mesenchymal cells, which form the body's supporting tissues. Soft tissue sarcomas are different from bone sarcomas such as osteosarcoma, see bone cancer, and from the much more common benign soft tissue lumps, such as lipomas.
Common types
| Type | Tissue | Typical features |
|---|---|---|
| Undifferentiated pleomorphic sarcoma | Unclear lineage | Older adults; often deep in the thigh |
| Liposarcoma | Fat | Thigh or retroperitoneum; several subtypes |
| Leiomyosarcoma | Smooth muscle | Abdomen, uterus, blood vessels |
| Synovial sarcoma | Not from the joint lining, despite the name | Young adults; near joints |
| Myxofibrosarcoma | Fibrous tissue | Older adults; limbs; tends to recur |
| Malignant peripheral nerve sheath tumor | Nerve sheath | Associated with neurofibromatosis type 1 |
| Rhabdomyosarcoma | Skeletal muscle | Most common sarcoma in children |
| Gastrointestinal stromal tumor (GIST) | Gut wall | Stomach or small intestine; targeted therapy |
| Kaposi sarcoma | Blood and lymph vessels | Purple skin lesions; linked to HHV-8 and weakened immunity |
| Dermatofibrosarcoma protuberans | Skin | Slow-growing skin plaque; rarely spreads |
Risk factors
Most sarcomas occur without a known cause. Recognized risk factors include:
- inherited syndromes: Li-Fraumeni syndrome, neurofibromatosis type 1, hereditary retinoblastoma, Gardner syndrome, Werner syndrome
- previous radiation therapy, usually years later in the treated area
- chronic lymphedema (Stewart-Treves syndrome)
- chemical exposures: vinyl chloride, some herbicides
- HHV-8 infection with weakened immunity, for Kaposi sarcoma
Injuries do not cause sarcomas, though an injury may draw attention to an existing lump.
Symptoms
- a lump or swelling, often painless, that grows over weeks to months
- pain if the tumor presses on nerves or muscles
- in the abdomen: swelling, fullness, early satiety, pain, constipation, or a lump felt only when large
- in the uterus: abnormal bleeding
- weight loss and fatigue in advanced disease
Features that suggest a lump may be a sarcoma
- larger than 5 cm (about the size of a golf ball)
- increasing in size
- deep to the fascia (under the muscle covering)
- painful
- recurring after removal
Most lumps with none of these features are benign, but any persistent lump deserves assessment.
Diagnosis
Lumps that might be sarcoma should be assessed before any surgery, ideally at a specialist sarcoma center, because an unplanned removal ("whoops" procedure) can make later treatment harder.
- Ultrasound as a first test for superficial lumps.
- MRI for limb and trunk tumors; CT for abdominal tumors.
- Core needle biopsy, planned by the treating team, to determine the subtype and grade.
- Chest CT to check for spread to the lungs, the most common site of metastasis.
- Molecular testing of the tumor, which helps identify subtypes and treatment options.
Staging and grade
Stage depends on tumor size, grade (how aggressive the cells look), spread to lymph nodes (uncommon) and distant spread. Grade is especially important in predicting outcome.
Treatment
Treatment is planned by a multidisciplinary sarcoma team.
- Surgery: wide removal of the tumor with a margin of healthy tissue is the main treatment. Limb-sparing surgery is possible in most limb sarcomas; amputation is rarely needed.
- Radiation therapy: before or after surgery to reduce local recurrence, particularly for larger, high-grade tumors.
- Chemotherapy: for some high-risk tumors, specific subtypes such as rhabdomyosarcoma, and advanced disease.
- Targeted therapy: for example, imatinib for GIST, and other targeted drugs for specific molecular changes.
- Immunotherapy: effective in some subtypes; clinical trials are often an option.
- Rehabilitation: physical and occupational therapy after limb surgery.
Follow-up
Regular follow-up with physical exams, imaging of the original site and chest scans continues for years, since recurrences can be late.
Outlook
Outcomes depend on subtype, grade, size, location and whether it has spread. Overall 5-year relative survival in the US is about 65%; it is around 80% or higher for localized tumors and lower when the cancer has spread. Treatment at high-volume sarcoma centers is associated with better outcomes.
Frequently asked questions
What are the warning signs of soft tissue sarcoma?
The most common sign is a lump that is growing, larger than 5 cm (2 inches), deep under the skin or muscle, or painful. Abdominal sarcomas can cause swelling, fullness or pain. Most lumps are benign, but persistent or growing lumps should be imaged.
How do I know if a lump is a lipoma or a sarcoma?
Lipomas are usually soft, small, superficial, movable and slow-growing. Lumps that are large, deep, firm, growing or painful are more concerning. Only imaging and, if needed, a biopsy can tell for sure.
Is soft tissue sarcoma curable?
Many soft tissue sarcomas are curable when found early and treated with surgery, often combined with radiation. Advanced or high-grade sarcomas are harder to cure, but treatment can control the disease, and new targeted therapies and trials offer additional options.
What is the survival rate for soft tissue sarcoma?
Overall 5-year relative survival in the US is about 65%. For sarcomas that have not spread beyond the original site, it is around 80% or higher. Survival is lower when the cancer has spread to distant organs.
Sources
This guide was written from current patient and clinical guidance, including:
- National Cancer Institute: Soft tissue sarcoma treatment (PDQ)
- American Cancer Society: Soft tissue sarcoma
- National Comprehensive Cancer Network: Soft tissue sarcoma guidelines for patients
- NICE: Suspected cancer, recognition and referral (sarcoma)
- Sarcoma Foundation of America: About sarcoma