Soft tissue sarcomas (liposarcoma, leiomyosarcoma, rhabdomyosarcoma) !

Rare cancers of fat, muscle and other connective tissue; most often a painless lump deep in the thigh that keeps growing.

Updated 2026-11-01

Structures involved

Tap one to see what it is and open it in 3D.

Why it happens

Show 4 more

What it is

A group of more than 50 malignant tumours that arise from mesenchymal tissue such as fat (liposarcoma), smooth muscle (leiomyosarcoma), skeletal muscle (rhabdomyosarcoma), fibrous tissue and nerve sheaths. They usually present as a deep mass in a limb, most often the thigh, and spread mainly through the blood to the lungs.

Who gets it

Rare, under 1% of adult cancers. About 45% arise in the limbs, many of the rest in the abdomen and retroperitoneum, the trunk and the head and neck. Liposarcoma and undifferentiated pleomorphic sarcoma are frequent in adults, leiomyosarcoma in the uterus and retroperitoneum, and rhabdomyosarcoma is the commonest soft tissue sarcoma of children. In Colombia, delays in referral of a 'lump' to a sarcoma centre are a recognised problem.

Causes

Most cases arise without a known cause
Previous radiotherapy to the area, often years earlier
Inherited syndromes: Li–Fraumeni (TP53), neurofibromatosis type 1 (malignant nerve sheath tumour) and hereditary retinoblastoma (RB1)
Chronic lymphoedema (lymphangiosarcoma, for example after breast cancer surgery)
Chemical exposures such as vinyl chloride, thorium dioxide and arsenic (hepatic angiosarcoma)

Risk factors

Prior radiation therapy
Family history suggesting Li–Fraumeni syndrome
Neurofibromatosis type 1
Long-standing lymphoedema
Childhood (rhabdomyosarcoma) or older age (most adult types)

Pathophysiology

Malignant mesenchymal cells grow along fascial planes, pushing aside muscle and forming a pseudocapsule that contains microscopic tumour extensions, which is why shelling out the lump causes local recurrence. Many subtypes carry characteristic chromosomal translocations (for example in synovial sarcoma, myxoid liposarcoma and alveolar rhabdomyosarcoma) or gene amplifications such as MDM2 in well-differentiated and dedifferentiated liposarcoma. Spread is mainly haematogenous to the lungs; lymph node spread is uncommon except in a few subtypes.

Classification

By tissue of origin: liposarcoma, leiomyosarcoma, rhabdomyosarcoma (embryonal, alveolar, pleomorphic), synovial sarcoma, undifferentiated pleomorphic sarcoma, malignant peripheral nerve sheath tumour and others
Histological grade 1–3 (differentiation, mitotic count and necrosis)
TNM staging by size, depth, grade, nodes and metastases
By site: extremity and trunk, retroperitoneal, visceral, head and neck

Symptoms and signs

Painless, enlarging lump, often deep to the fascia
Pain or swelling only when the mass presses on nerves or vessels
Abdominal fullness or vague pain with retroperitoneal tumours, which can grow very large
In children with rhabdomyosarcoma: a mass in the head and neck, orbit or genitourinary tract
Cough or breathlessness only with lung metastases

Diagnosis

Clinical: Every deep or large or growing soft tissue lump is treated as a possible sarcoma until proved otherwise and referred to a sarcoma team before any surgery. An unplanned excision ('whoops' operation) contaminates tissue planes and worsens outcomes.
Tests: Image-guided core needle biopsy, planned so the tract can be removed at surgery, with review by an expert pathologist using immunohistochemistry and molecular tests (for example MDM2 amplification or specific translocations). Grade is set on the biopsy.
Imaging: MRI of the primary site to define size, depth and relation to nerves and vessels; CT of the chest to look for lung metastases; CT of the abdomen and pelvis for retroperitoneal tumours; PET-CT in selected cases.

Differential diagnosis

Lipoma and other benign soft tissue tumours
Haematoma, especially in a patient taking anticoagulants
Abscess
Bone sarcoma with soft tissue extension (osteosarcoma, Ewing sarcoma)
Lymphoma or metastatic carcinoma in soft tissue
Myositis ossificans

Goal of treatment

Remove the tumour completely with a wide margin while keeping the limb and its function, and reduce the risk of local and distant recurrence.

Treatment

Surgical: Wide excision with a cuff of normal tissue, preserving the limb in most cases; amputation is reserved for tumours that cannot otherwise be removed.
Procedure: Radiotherapy before or after surgery for high-grade, large or deep tumours, or when margins are close, to reduce local recurrence.
Medical: Chemotherapy (anthracycline-based, sometimes with ifosfamide) for advanced or metastatic disease and selected high-risk tumours; multi-agent chemotherapy is standard for rhabdomyosarcoma in children. Some subtypes respond to targeted drugs.
Follow-up: Follow-up with clinical examination, imaging of the operated site and chest imaging, most intense in the first few years; rehabilitation for limb function.

Complications

Local recurrence, more likely after unplanned or marginal excision
Lung metastases
Wound complications and fibrosis after radiotherapy and surgery
Loss of limb function or amputation
Cardiotoxicity from anthracyclines

Prognosis

Small, superficial, low-grade tumours are often cured by surgery alone. Large, deep, high-grade tumours, age over 60 and positive margins carry a higher risk of lung metastases and death; resection of a few lung metastases can still give long survival in selected patients.

Test yourself

Think of the answer, then tap the question to see it.

What is the commonest site of soft tissue sarcoma in adults?

The limbs, especially the thigh.

Where do soft tissue sarcomas most often metastasise?

To the lungs, through the bloodstream.

How should a deep soft tissue mass larger than 5 cm be investigated?

MRI and an image-guided core biopsy planned by a sarcoma team before any excision.

Which is the most common soft tissue sarcoma in children?

Rhabdomyosarcoma.

Which inherited syndromes predispose to soft tissue sarcomas?

Li–Fraumeni syndrome (TP53) and neurofibromatosis type 1, among others.

Add to my cards (5)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: Soft Tissue Sarcoma Treatment (PDQ®)–Health Professional Version (National Cancer Institute, 2025).

← All conditions

Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake

Representative model, for educational purposes only.

Vastus lateralis highlighted on the Durgical 3D model