Approved by the Cancer.Net Editorial Board, 06/2022
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 and typically do not affect a person’s life span.
What are 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 in adults, accounting for about 1% of all adult cancers. 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
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 in adults, accounting for about 1% of all adult cancers. 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 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, soft-tissue sarcomas can occur almost anywhere in the body. When a soft-tissue sarcoma begins and is small, it can go unnoticed because it usually does not cause problems, such as pain. However, as a sarcoma grows, it can cause pain or interfere with the body’s normal functions.
Not all sarcomas are the same. Because there are more than 70 different types of soft-tissue sarcoma 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, so they are named by what they look like under the microscope or according to their genetics rather than the tissues they are suspected to have started in.
The list below describes several common types of soft-tissue sarcoma and related connective tissue tumors.
| Name of Sarcoma | Related Normal Tissue Type or Affected Body Part |
|---|---|
| Adenosarcoma | Uterus |
| Angiosarcoma | Blood or lymph vessels |
| Aveolar soft part sarcoma | No obvious related normal tissue |
| Dermatofibrosarcoma protuberans | Skin |
| Desmoid tumor, also called deep fibromatosis | Fibroblasts, which are the most common type of cells in connective tissue |
| Embryonal sarcoma | Liver |
| Endometrial stromal sarcoma | Uterus |
| Epithelioid hemangioendothelioma | Blood vessels in liver or lungs |
| Ewing family of tumors | No obvious related normal tissue; may be a tumor of stem cells |
| Fibrosarcoma | Fibroblasts |
| Follicular dendritic cell tumor | Lymph nodes or other lymphatic tissue |
| Gastrointestinal stromal tumor (GIST) | Specialized neuromuscular cells of the digestive tract |
| Interdigitating cell tumor | Lymph nodes or other lymphatic tissue |
| Intimal sarcoma | Aorta, pulmonary artery or vein (large blood vessels coming in and out of the heart) |
| Kaposi sarcoma | Blood vessels |
| Leiomyosarcoma | Smooth muscle |
| Liposarcoma | Fat tissue |
| Lymphangioleiomyomatosis | Lymph nodes or other lymphatic tissue |
| Myxofibrosarcoma | No obvious related normal 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 |
| Perivascular epithelial cell tumor (PEComa) | Lymph nodes or other lymphatic tissue |
| Phyllodes tumor | Breast |
| Pleomorphic dermal sarcoma | Skin |
| Prostatic stromal sarcoma | Prostate |
| Rhabdomyosarcoma | Skeletal muscle |
| Solitary fibrous tumor | No obvious related normal tissue |
| Synovial sarcoma | No obvious related normal tissue |
| True histiocytic sarcoma | Lymph nodes or other lymphatic tissue |
| Undifferentiated endometrial sarcoma | Uterus |
| Undifferentiated pleomorphic sarcoma (UPS), previously called malignant fibrous histiocytoma (MFH) | No obvious related normal tissue |
When a tumor is found and the doctor believes it could be sarcoma, it is important to find out the specific 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 histology. Sometimes they need more information and additional molecular and 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.
Some sarcomas are relatively slow growing. Others can grow quite quickly. For example, phyllodes tumors can grow quickly but, unlike most common breast cancers, only very rarely spread to lymph nodes.
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.
