Soft tissue sarcoma is metastatic if it has spread to areas in the body away from the location of the original tumor.

Soft tissue sarcoma may spread through the bloodstream or lymphatic system to other areas of the body.

Doctors may detect metastatic soft tissue sarcoma at the initial diagnosis or before finding the original tumor.

Treatment may include surgery where possible, radiation therapy, chemotherapy, and other drug treatments, such as targeted therapies.

This article outlines the diagnosis, treatment, and outlook for metastatic soft tissue sarcoma.

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Metastatic soft tissue sarcoma is soft tissue sarcoma that has spread to distant areas of the body. Doctors may refer to this as stage 4 sarcoma.

In metastatic soft tissue sarcoma, the cancer cells have broken away from the original, primary tumor and spread to other areas through the bloodstream or lymphatic system.

Even if soft tissue sarcoma spreads to another area, such as the lungs or bones, it is still soft tissue sarcoma rather than lung or bone cancer.

According to a 2018 article, around 83% of metastatic soft tissue sarcoma occurs in the lungs. Around 25% of metastatic soft tissue sarcoma cases may occur after initial treatment for the primary tumor.

Doctors may use a biopsy to diagnose metastatic soft tissue sarcoma. A core biopsy may be more accurate than a fine-needle aspiration. Doctors may also use an incisional biopsy to carry out laboratory tests for diagnosis.

A core biopsy uses a wide needle to remove multiple tissue samples for laboratory testing. Doctors may use imaging tests, such as ultrasound, to help guide this procedure. An incisional biopsy removes a tissue sample or part of a lump for laboratory testing.

Laboratory tests can help doctors gather specific information about the tissue sample when looking for signs of cancer, including features such as:

  • the appearance and number of cells
  • certain genes and proteins
  • changes in chromosomes
  • certain antigens

Doctors may also order the following tests to help them stage cancer and find out if and where it has spread:

Along with biopsy results, these tests can help doctors stage cancer and decide on appropriate treatment.

Learn more about biopsies here.

Treatment depends on the specific type of soft tissue sarcoma but may involve surgery, chemotherapy, radiation therapy, and targeted therapies.

Doctors may try to remove all or most of the primary and metastatic soft tissue sarcoma with surgery.

If surgery does not completely remove the cancer, people may also have radiation therapy or chemotherapy to help shrink and destroy the tumors.

Chemotherapy for treating soft tissue sarcoma may include the drugs doxorubicin and ifosfamide. If these are not effective, people may have gemcitabine and docetaxel.

The type of chemotherapy drugs may also depend on the type of sarcoma people have. People with angiosarcomas may have treatment with paclitaxel or docetaxel and vinorelbine.

Targeted therapies specifically target cancer cells to destroy them, which may reduce damage to healthy tissue. Targeted therapy or immunotherapy may benefit people with certain types of soft tissue sarcoma.

Targeted therapy drugs for soft tissue sarcoma may help prevent cancer cells from growing. They include tyrosine kinase inhibitors and histone methyltransferase inhibitors.

Immunotherapy drugs help the immune system destroy cancer cells better. They include immune checkpoint inhibitors.

Learn more about soft tissue sarcoma treatment here.

A soft tissue sarcoma may first appear as a painless swelling or lump under the skin. Primary soft tissue sarcomas usually develop in an arm or leg but can also affect other areas, such as the abdomen.

As a sarcoma gets bigger, it may press on surrounding nerves, blood vessels, or organs, and people may experience pain or difficulty breathing.

In some instances, people with metastatic soft tissue sarcoma may not experience any symptoms.

Metastatic cancer may cause additional symptoms, such as:

According to the American Cancer Society (ACS), doctors may cure metastatic soft tissue sarcoma if they can completely remove the primary and metastatic sarcoma with surgery.

The best outlook for a person with metastatic soft tissue sarcoma may be for cancer that has spread to the lungs only. In this case, doctors will remove the metastatic sarcoma completely if they can and treat the primary sarcoma as they would a stage 2 or stage 3 sarcoma.

A relative survival rate suggests how long a person with a particular condition will live after receiving a diagnosis compared with those without the condition.

According to the ACS, the 5-year relative survival rate for people with metastatic soft tissue sarcoma between 2010–2016 was 15%. This means a person with this cancer is 15% as likely to live for 5 years as someone without the condition. More recent data has yet to be released so the outlook may be better now than it was.

Other factors also affect outlook, such as:

  • the location of metastases and how far the cancer has spread
  • tumor grade
  • location of the primary tumor
  • cancer response to treatment
  • age and overall health of the person

Learn more about the outlook for soft tissue sarcoma here.

Metastatic soft tissue sarcoma means cancer cells from the original tumor have spread to distant areas of the body.

The outlook may depend on various factors, such as where the cancer has spread, tumor grade, treatment response, and overall health.