Delimiter Image

Recently Diagnosed?

Learn About Epithelioid Sarcoma

What is Epithelioid Sarcoma?

Sarcomas are a rare type of cancer that occur in hard tissues, like bone, or soft tissues, like muscle. Sarcomas that form in soft tissues—like muscle, fat, nerves, fibrous tissues (connecting muscle and bone), blood vessels and deep skin tissues—are called soft tissue sarcomas (STS). If you have recently been diagnosed with STS, it’s important to ask your doctor what type you have. There are more than 50 types of STS, of which epithelioid sarcoma (ES) is one type.

Rare Cancer

Click image to enlarge

ES is ultra-rare and accounts for less than 1 percent of all STS. Approximately 150-200 people in the U.S. are newly diagnosed annually with ES.

ES can affect people of all ages and genders. However, ES is more common in men and young adults.

While the cause of ES is unknown, the following factors may contribute to the risk of developing ES:

  • Exposure to radiation, including radiation therapy for other types of cancer
  • A hereditary or genetic predisposition for sarcoma

A rare cancer in the U.S. is defined as fewer than 15 new diagnoses per 100,000 people per year.

Forms of ES

ES typically occurs as a hard lump in the soft tissue under the skin of a finger, hand, forearm, lower leg or foot, though it can start in other areas of the body as well, such as the torso. There are two forms of ES – distal-type and proximal-type.

1: Distal-type
Is the standard form of ES and typically affects teenagers and young adults. It is typically associated with more favorable survival rates. Distal-type ES typically occurs in the hands, forearms, feet or ankles.

2: Proximal-type
Is the rarer, more aggressive form of ES and mainly affects older adults. It is typically associated with less favorable survival rates. Proximal-type ES typically occurs in the pelvic area or abdomen.

Signs & Symptoms

ES may grow slowly and painlessly without any signs or symptoms. However, because each experience is unique, some people with ES may occasionally have pain and tenderness, among other symptoms.

At first, ES may be mistaken for other conditions and treated as such, including:

  • A benign growth, such as an ulcer, abscess or infected wart
  • A malignant (cancerous) growth, such as melanoma
  • A wound that won’t heal

Following a diagnosis of ES, it is important to find a healthcare professional who specializes in treating soft tissue sarcomas (specialist), which means they may be more knowledgeable about diagnosing and treating ES.


Since ES is an ultra-rare form of sarcoma, it can be difficult to diagnose. Your doctor may do any of the following to diagnose ES:

Physically examine the area of concern

Order a scan (a local MRI, whole-body CT scan or ultrasound)

Take a biopsy of the area and send it to the lab for testing. If cancer is found, your physician may send the sample for further testing to determine tumor subtype

Because ES is often mistaken for more common conditions – such as a benign growth or a bump – tumors may be removed surgically and analyzed before a diagnosis is made.

  • During surgery, the surgeon may take a biopsy of the tumor, which is often sent to a lab for testing to correctly identify the lump.
  • At the lab, a pathologist will analyze the biopsy tissue under a microscope to see if the lump is cancerous.
  • In the case of ES, the pathologist will look to see if the tumor cell patterns match those commonly observed in ES. If they do match, then the pathologist will make a definitive diagnosis.
  • When reviewing an ES tumor, a pathologist might identify the loss of the INI1 protein, which is common in both distal- and proximal-type ES cases. Identifying INI1 protein loss can help pathologists confirm a diagnosis of ES. This information will be included in the pathology report which is sent to your oncologist.

Before receiving a formal diagnosis of ES, it’s common to receive an incorrect diagnosis (misdiagnosis) for several reasons, including:

  • It’s ultra-rare, and may not be top-of-mind for many doctors (fewer than 15 new diagnoses per 100,000 people per year in the U.S.).
  • It can look harmless when it first forms and may be mistaken for non-cancerous conditions which do not require a biopsy.
  • It often occurs in young adults in their 20s and 30s, unlike most cancers that are usually diagnosed in adults age 55 years or older.

As with any type of cancer, early diagnosis is key, as earlier treatment can result in more favorable outcomes.

Receiving a diagnosis of ES can be scary, but you’re not alone. There are resources and information available to support you.


ES can be diagnosed at any of the following stages of the disease, including:

Stage 1 – Localized: the cancer is only in one primary spot and the nearby tissue

Stage 2-3 – Regional: the cancer has begun to spread to nearby lymph nodes, other tissue or organs

Stage 4 – Metastatic: the cancer has spread beyond the primary spot and nearby tissue to distant parts of the body

Your ES Care Team will work with you to create a customized ES treatment plan based on the stage and other factors.

References: Click to Expand
  1. About Soft Tissue Sarcoma: What Is a Soft Tissue Sarcoma? American Cancer Society. Updated April 6, 2018. Accessed January 9, 2019. Available at:
  2. Armah, H.B. Arch Pathol Lab Med. 2009;133(5):814–819. Available at:
  3. SEER*Stat Database, 1973-2014
  4. NCI Dictionary of Cancer Terms. National Cancer Institute. Accessed Jan 15, 2019. Available at:
  5. Sobanko JF, et al. Epithelioid Sarcoma: A Review and Update (Table 3). J Clin Aesthet Dermatol. 2009 May; 2(5): 49–54. Available at:
  6. Guillou L and Kaneko Y. Epithelioid Sarcoma. In CDM Fletcher, KK Unni, & F Mertens, eds. Pathology and Genetics of Tumours of Soft Tissue and Bone. Lyon, France: IARC Press; 2002:205–207. Available at:
  7. Hui JY. Surg Clin North Am. 2016;96(5):901–914. Available at:
  8. Rare Cancers in Adults, 2017. American Cancer Society. Accessed Jan 15, 2019. Available at:
  9. Jawad MU, et al. Clin Orthop Relate Res. 2009;467(11), 2939-2948. Available at:
  10. Epithelioid sarcoma. Mayo Clinic. Updated May 26, 2018. Accessed March 27, 2019. Available at:
  11. Needs T, Fillman EP. Cancer, Sarcoma, Epithelioid. StatPearls. Treasure Island. 2019. Available at
  12. Guzzetta AA, Montgomery EA, Lyu H, et al. Epithelioid sarcoma: one institution’s experience with a rare sarcoma. J Surg Res. 2012;177(1):116-22. Available at
  13. Cancer Surgery: Physically Removing Cancer, Mayo Clinic. Updated November 2018. Accessed April 2019. Available at
  14. Modena, Piergiorgio, et al. SMARCB1/INI1 Tumor Suppressor Gene Is Frequently Inactivated in Epithelioid Sarcomas. May 2005. Available at:
  15. DeSantis CE, et al. The Burden of Rare Cancers in the United States. CA: A Cancer Journal for Clinicians. 2017 May; 67(4), 261-272. Available at:
  16. American Cancer Society. Cancer Facts & Figures 2019. Accessed Mar 11, 2019. Available at:
  17. Treatments of Soft Tissue Sarcomas, by Stage. American Cancer Society. Last updated April 2018. Accessed April 2019. Available at
  18. What is Metastatic Cancer? National Cancer Institute. Accessed January 9, 2019. Available at: