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Cancer starts when cells start to grow out of control. Cells in nearly any part of the body can become cancer and can spread to other areas. To learn more about how cancers start and spread, see What Is Cancer?
There are many types of soft tissue tumors, and not all of them are cancerous. Many benign tumors are found in soft tissues. The word benign means they're not cancer. These tumors can't spread to other parts of the body. Some soft tissue tumors behave in ways between a cancer and a non-cancer. These are called intermediate soft tissue tumors.
When the word sarcoma is part of the name of a disease, it means the tumor is malignant (cancer). A sarcoma is a type of cancer that starts in tissues like bone or muscle. Bone and soft tissue sarcomas are the main types of sarcoma. Soft tissue sarcomas can develop in soft tissues like fat, muscle, nerves, fibrous tissues, blood vessels, or deep skin tissues. They can be found in any part of the body. Most of them start in the arms or legs. They can also be found in the trunk, head and neck area, internal organs, and the area in back of the abdominal (belly) cavity (known as the retroperitoneum). Sarcomas are not common.
Sarcomas that most often start in bones, such as osteosarcomas, and sarcomas that are most often seen in children, such as the Ewing family of tumors and rhabdomyosarcomas, are not covered here.
There are more than 50 different types of soft tissue sarcomas. Some are quite rare, and not all are listed here:
These tumors may grow and invade nearby tissues and organs, but they tend to not spread to other parts of the body.
Many benign (non-cancerous) tumors can start in soft tissues. These include:
Spindle cell tumor and spindle cell sarcoma are descriptive names used when tumor cells look long and narrow under the microscope. Spindle cell tumor is not a specific diagnosis or a specific type of cancer. The tumor may be a sarcoma, or it can be sarcomatoid — meaning another type of tumor (like a carcinoma) that looks like a sarcoma under the microscope.
Some changes in soft tissues are caused by inflammation or injury and can form a mass that looks like a soft tissue tumor. Unlike a real tumor, they don't come from a single abnormal cell, they have limited ability to grow or spread to nearby tissues, and they never spread to other parts of the body. Nodular fasciitis and myositis ossificans are 2 examples. They affect tissues under the skin and muscle tissues, respectively.
The American Cancer Society medical and editorial content team
Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.
Helman LJ, Maki RG. Sarcomas of soft tissue. In: Niederhuber JE, Armitage JO, Doroshow JH, Kastan MB, Tepper JE. Abeloff‘s Clinical Oncology. 5th ed. Philadelphia, PA. Elsevier: 2014: 1753-1791.
MacNeill AJ, Gupta A, Swallow CJ. Randomized Controlled Trials in Soft Tissue Sarcoma: We Are Getting There! Surg Oncol Clin Am. 2017;26:531-544.
Medscape. Benign and Malignant Soft-Tissue Tumors. March 27, 2017. Accessed at https://emedicine.medscape.com/article/1253816-overview on March 27, 2018.
National Comprehensive Cancer Network, Clinical Practice Guidelines in Oncology (NCCN Guidelines®), Soft Tissue Sarcoma, Version 1.2018 -- October 31, 2017. Accessed at www.nccn.org/professionals/physician_gls/pdf/sarcoma.pdf on March 27, 2018.
Singer S, Maki R, O’Sullivan B. Soft tissue sarcoma In: DeVita VT, Heilman S, Rosenberg SA, eds. Cancer: Principles and Practice of Oncology. 9th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2011:1533-1577.
Villalobos VM, Byfield SD, Ghate SR, Adejoro O. A retrospective cohort study of treatment patterns among patients with metastatic soft tissue sarcoma in the US. Clin Sarcoma Res. 2017;7:18.
Last Revised: November 23, 2021
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