Sarcomas, Soft Tissue: Introduction

Approved by the Cancer.Net Editorial Board, 11/2020

ON THIS PAGE: You will find some basic information about this disease and the parts of the body it may affect. This is the first page of Cancer.Net’s Guide to Soft-Tissue Sarcomas. Use the menu to see other pages. Think of that menu as a roadmap for this complete guide.

Cancer begins when healthy cells change and grow out of control, forming a mass called a tumor. A tumor can be cancerous or benign. A cancerous tumor is malignant, meaning it can grow and spread to other parts of the body. A benign tumor means the tumor can grow and invade nearby structures but will not spread.

About sarcomas

Sarcomas are cancers that develop from bones or soft tissues, such as fat, muscles, nerves, and more. Because bone and soft tissues can be found nearly everywhere in the body, a sarcoma can start in any part of the body.

  • 60% begin in an arm or leg

  • 30% start in the torso or abdomen

  • 10% occur in the head or neck

Both children and adults can develop a sarcoma. It is rare, accounting for about 1% of all adult cancers. However, sarcomas represent about 15% of all childhood cancers.

This section covers sarcomas of the soft tissues. Learn more about sarcoma that starts in bones.

About soft-tissue sarcomas

Soft-tissue sarcomas (STS) are a group of cancers that begin in the connective tissues that support and connect the body, including:

  • Blood vessels

  • Fat cells

  • Lining of joints

  • Lymph vessels

  • Muscle

  • Nerves

  • Tendons

As a result, STS can occur almost anywhere in the body. When an STS begins and is small, it can go unnoticed because it usually does not cause problems, such as pain. However, as an STS grows, it can cause pain or interfere with the body's normal functions.

Not all sarcomas are the same. Because there are more than 50 different types of STS and each has a different natural history – meaning where they start, how they affect the body, how fast they grow, and how they respond to treatment – it is more accurate to describe them as a family of related diseases rather than as a single disease.

Specific types of sarcoma are often named according to the normal tissue cells they most closely resemble, as listed below. This is different from most other types of cancer, which usually are named for the part of the body where the cancer began. Some sarcomas do not look like any type of normal tissue and are thought to come from stem cells or other primitive cells. Stem cells are special cells that can mature into specific tissues or organs.

The list below describes several common types of STS and related connective tissue tumors.

Name of Sarcoma

Related Normal Tissue Type

Angiosarcoma

Blood or lymph vessels

Desmoid tumor, also called deep fibromatosis

Fibroblasts, which are the most common type of cells in connective tissue

Ewing family of tumors

No obvious related normal tissue; may be a tumor of stem cells

Fibrosarcoma

Fibroblasts, which are the most common type of cells in connective tissue

Gastrointestinal stromal tumor (GIST)

Specialized neuromuscular cells of the digestive tract

Kaposi sarcoma

Blood vessels

Leiomyosarcoma

Smooth muscle

Liposarcoma

Fat tissue

Myxofibrosarcoma

Connective tissue

Malignant peripheral nerve sheath tumor (MPNST), also known as neurofibrosarcoma

Cells that wrap around nerve endings, similar to the way insulation wraps around a wire

Rhabdomyosarcoma

Skeletal muscle

Synovial sarcoma

No obvious related normal tissue; may be a tumor of stem cells

Undifferentiated pleomorphic sarcoma (UPS), previously called malignant fibrous histiocytoma (MFH)

No obvious related normal tissue; may be a tumor of stem cells or a distant relative of rhabdomyosarcoma

When a tumor is found and the doctor believes it could be sarcoma, it is important to find out the type of sarcoma as part of the diagnosis process. Because there are so many different types of sarcomas, it is best if an expert pathologist who specializes in sarcoma examines the tumor sample. A pathologist is a doctor who uses a microscope to look at the tumor specimen to make the diagnosis. The pathologist will look under the microscope to see the size and shape (called morphology) of the tumor cells and do special stains (called immunohistochemistry) to determine what type of sarcoma it is (this is called the histology). Sometimes they need more information and additional genetic tests are performed, which take longer for the results to come back. Pathologists are looking for new ways to quickly determine a tumor's type because this helps the health care team decide on the best treatment plan.

Pathologists also describe a sarcoma by its “grade,” which describes how closely cancer cells look or don’t look like healthy cells when viewed under a microscope. A higher-grade tumor has cells that look more abnormal and are potentially more aggressive. The grade can help the doctor predict how quickly the sarcoma will grow and spread. In general, a lower-grade tumor is less likely to come back after treatment and more likely to grow slower than a higher-grade tumor. A pathologist with expertise in sarcomas should be involved when the doctor suspects the diagnosis will be a sarcoma. Learn more about grade in the Stages and Grades section.

Looking for More of an Introduction?

If you would like more of an introduction, explore these related items. Please note that these links will take you to other sections on Cancer.Net:

The next section in this guide is Statistics. It helps explain the number of people who are diagnosed with sarcoma and general survival rates. Use the menu to choose a different section to read in this guide.