Soft-Tissue Sarcoma

Soft-tissue sarcoma (STS) is a malignant tumour that develops in soft tissues. These tumours are often painless and grow slowly over months or years. They can be superficial or deep-seated, and any unexplained mass should be diagnosed by biopsy. Treatment options include surgery, radiotherapy, chemotherapy, and targeted drug therapy. Bone sarcomas are another class of sarcomas.

Types

Soft-tissue sarcomas are diverse, with over fifty subtypes listed by the World Health Organisation. Major types in adults include undifferentiated pleomorphic sarcoma, dermatofibrosarcoma protuberans, synovial sarcoma, liposarcoma, rhabdomyosarcoma, leiomyosarcoma, angiosarcoma, Kaposi sarcoma, malignant peripheral nerve sheath tumour, extraskeletal myxoid chondrosarcoma, and extraskeletal osteosarcoma.

In children, common types include embryonal and alveolar rhabdomyosarcoma, alveolar soft part sarcoma, leiomyosarcoma, undifferentiated pleomorphic sarcoma, dermatofibrosarcoma protuberans, synovial sarcoma, liposarcoma, malignant peripheral nerve sheath tumours, and extraskeletal myxoid chondrosarcoma.

Signs and Symptoms

In early stages, soft-tissue sarcomas usually do not cause symptoms. Tumours can become quite large before causing problems, as soft tissue is relatively elastic. The first noticeable symptom is often a painless lump or swelling. As the tumour grows, it may press against nearby nerves and muscles, causing pain or soreness. Abdominal tumours can cause symptoms like abdominal pain, menstrual-like cramps, indigestion, or constipation.

Risk Factors

Most soft-tissue sarcomas are not associated with known risk factors. However, some exceptions include:

• Occupational exposure: Workers exposed to chlorophenols, phenoxy herbicides, or vinyl chloride may have an increased risk.
• Radiation exposure: Patients treated with high doses of radiation in the early 1900s for noncancerous conditions developed soft-tissue sarcomas.
• Viral infections: Kaposi sarcoma is caused by human herpesvirus 8 and often occurs in patients with AIDS.
• Genetic factors: Conditions like Li-Fraumeni syndrome, neurofibromatosis type I, and inherited retinoblastoma increase the risk.

Diagnosis

The only reliable way to diagnose soft-tissue sarcoma is through a biopsy, either needle aspiration or surgical incision. A pathologist examines the tissue under a microscope to determine the presence, type, and grade of cancer. Grading systems include the National Cancer Institute system and the French Federation of Cancer Centres Sarcoma Group system. Sarcomas commonly originate in the upper body and may spread to the lungs.

Treatment

Treatment depends on the stage of the cancer, based on tumour size, grade, and spread. Options include:

• Surgery: The most common treatment, involving removal of the tumour with surrounding healthy tissue.
• Radiotherapy: Used before surgery to shrink tumours, after surgery to kill remaining cells, or for inoperable tumours.
• Chemotherapy: Used with radiotherapy to shrink tumours or kill remaining cells. Doxorubicin may reduce recurrence, and docetaxel plus gemcitabine may be effective for advanced cases.
• Targeted drug therapy: Investigated in various subtypes of sarcomas.

Research

Research in soft-tissue sarcoma is challenging due to its rarity, requiring significant collaboration. Immunotherapy shows promise, with regulatory approval for atezolizumab in alveolar soft part sarcoma. The Immunological Constant of Rejection (ICR) signature is a notable area of research, showing prognostic value and potential for tailored therapies.

Epidemiology

Soft-tissue sarcomas are rare, accounting for less than 1% of new cancer cases annually. In 2023, about 14,300 new cases were diagnosed in the United States. They are more common in older patients, but certain types are prevalent in children and adolescents. In the UK, around 3,300 cases were diagnosed in 2011.

Notable Cases

• Actor Robert Urich (synovial sarcoma)
• Actress Michelle Thomas (desmoplastic small-round-cell tumour)
• Evangelist Henry Feyerabend (sarcoma)
• Video game artist Adam Adamowicz (muscle sarcoma)
• Wrestler Zack Ryder (synovial sarcoma)
• India's ex-finance minister Arun Jaitley (sarcoma)
• Writer Rachel Caine (sarcoma)
• YouTuber Technoblade (sarcoma)

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Self-assessment MCQs (single best answer)

What is the most common initial symptom of soft-tissue sarcomas?

Which of the following is a genetic condition associated with an increased risk of soft-tissue sarcoma?

Which type of sarcoma is caused by human herpesvirus 8?

What is the most common treatment method for soft-tissue sarcomas?

Soft-tissue sarcomas account for what percentage of new cancer cases annually?

Which of the following treatments may be used before surgery to shrink tumours?

What year did the UK diagnose approximately 3,300 cases of soft-tissue sarcoma?

Who among the following was diagnosed with synovial sarcoma?

Which medication is mentioned as a potential treatment to reduce recurrence of soft-tissue sarcoma?

Which risk factor is NOT associated with an increased risk of soft-tissue sarcoma?