Clear cell sarcoma

A clear cell sarcoma (CCS) is a malignant (cancerous) tumor that typically grows superficially, or just under the skin. CCS tumors are usually found near muscle coverings called sheaths. They can also occur near tendons, the connections between muscles and bones.

The most common locations for CCS are the legs, ankles, hands, and feet. Tumors occasionally form in the head and neck, genitals, gastrointestinal (GI) tract, chest, abdomen (belly), pelvis, and back. CCS may also occur as an unusual pediatric kidney cancer called clear cell sarcoma of the kidney.

CCS is extremely rare. These tumors mainly affect people in their 20s, 30s, or 40s. They account for just 1 percent of soft tissue sarcomas. Even with effective care, clear cell sarcomas can return or spread (metastasize) many years after initial treatment. Metastasis may be widespread in the body, with lymph nodes, lungs, and bones the most common locations for tumors.

The Sarcoma Program at Penn Medicine’s Abramson Cancer Center has one of the nation’s most experienced teams in CCS care. Our surgeons can often save arms and legs affected by the disease and perform sophisticated operations elsewhere in the body.

A clear cell sarcoma may not cause symptoms right away. As these tumors grow larger, you may experience symptoms such as:

• Lump under skin that sometimes causes pain, swelling, or tenderness
• Rare ulcers (open wounds) in which CCS affects the skin
• Fatigue

Clear cell sarcomas form because of changes in chromosomes—the structures inside cells that are made of DNA. With clear cell sarcoma, two genes in DNA swap places and recombine. The new genes function differently than they should and appear to promote cancer. Researchers don’t yet know why the chromosomal swap happens with CCS. This gene change (also called a variant or mutation) cannot be passed down to children.

For other soft tissue sarcomas, gene changes related to cancer are sometimes caused by exposure to certain chemicals, previous medical treatments, or unusual inherited genetics. It’s unclear if any of these risk factors apply to clear cell sarcoma.

Doctors currently do not know of any steps you can take to reduce your risk of developing a clear cell sarcoma.

The most accurate diagnosis of a clear cell sarcoma comes from an experienced cancer team like the one at Penn Medicine. Because the disease has similarities to the skin cancer melanoma, the shared features require a thorough evaluation by an experienced team who knows what to look for with a suspected tumor. In fact, the diseases are so similar that CCS was previously called “malignant melanoma of soft parts.”

To diagnose a potential clear cell sarcoma, our team starts by examining any lumps and asking you about symptoms you’ve experienced. Imaging scans then provide the team with more information. Magnetic resonance imaging (MRI) can show the size of the tumor, how far it has grown, and which tissues it has affected. Computed tomography (CT) can show whether cancer has spread and, if so, to which locations.

To confirm a diagnosis, our specialized radiologists perform an image-guided needle biopsy. We take a sample of tumor tissue, study it under a microscope, and run lab tests on it. By testing for genetic changes, those lab tests can confirm whether a tumor is clear cell sarcoma or something else.

Information from the exam, scans, and biopsy helps us stage clear cell sarcoma. Staging is a more detailed description and categorization of the cancer that helps guide our treatment planning, for the most effective approach.

When clear cell carcinoma has not spread, our treatment focuses on surgically removing the tumor. As with sarcoma surgery for other tumor types, the best results come from taking the clear cell sarcoma out in one piece, along with a border of healthy tissue. Prognosis depends on:

• Tumor size and location
• Patient age and overall health
• Ability of surgeon to take out all the cancer

To reduce the chance that cancer recurs (returns), we may recommend adding radiation therapy, before or after surgery. Undergoing radiation therapy before surgery provides the advantage of reducing the side effects of treatment.

Clear cell sarcoma often comes back after treatment—either to the same spot or metastasized to other locations in the body. After you complete treatment, our team will recommend regular checkups to watch for cancer recurrence.

At Penn Medicine, we continue to explore new ways to effectively treat soft tissue sarcomas, including limb-sparing surgery for clear cell sarcomas in the arms and legs.