Epithelioid sarcoma (ES) is a rare form of soft tissue cancer that develops from mesenchymal tissue, accounting for less than 1% of all soft tissue sarcomas. It was first clearly described in 1970 and often affects young adults, though it can occur at any age. While slow-growing, ES can be aggressive and has a tendency for local recurrence and spread to regional lymph nodes and distant sites. Early detection is important for better outcomes.
Recognizing Early Indicators
The initial signs of epithelioid sarcoma can be subtle, often appearing as a small lump or nodule beneath the skin. These growths are firm to the touch and may not cause pain or tenderness in their early stages, which can lead to delayed recognition. The most common locations for these lumps are the extremities, particularly the fingers, hands, forearms, lower legs, and feet.
Multiple lumps may develop in the affected area, or the skin over the lump might ulcerate, forming a sore that does not heal. This ulceration can be mistaken for a poorly healing wound or a wart, complicating early diagnosis. While the tumor grows slowly, over months or even years, any new or changing lump, especially on the limbs, warrants medical evaluation.
Diagnosis and Staging
Diagnosis of epithelioid sarcoma begins with a physical examination to assess suspicious lumps or swellings. Imaging determines the tumor’s size, location, and spread. MRI is used for detailed soft tissue visualization. CT scans, particularly of the chest, check for distant spread, such as to the lungs. PET scans may also be used for comprehensive staging and to assess metabolic activity.
A definitive diagnosis relies on a tissue biopsy, where a tumor sample is removed for laboratory analysis. This can be a core needle biopsy, preferred for its accuracy and low complication rate, or an incisional or excisional biopsy. Pathologists examine the tissue under a microscope. Immunohistochemistry identifies specific protein markers, such as the loss of INI1 (SMARCB1) protein, which is characteristic of epithelioid sarcoma and helps distinguish it from other conditions. Staging assesses the tumor’s size and spread to nearby lymph nodes or distant parts of the body, classifying it as localized or metastatic.
Treatment Strategies
Surgical removal is the primary treatment for localized epithelioid sarcoma and represents the only potentially curative approach. Surgeons aim to remove the tumor along with a surrounding margin of healthy tissue to reduce the likelihood of local recurrence. While wide margins are pursued, efforts are made to preserve limb function, especially given the common location of these tumors on the extremities.
Radiation therapy is used in conjunction with surgery, either before (neoadjuvant) or after (adjuvant) the procedure, for larger tumors, those with close or positive margins, or a high risk of recurrence. This local treatment uses high-energy radiation to target and destroy any remaining cancer cells. Systemic therapies, such as chemotherapy, are considered for more advanced cases, including widespread disease or aggressive features. Their effectiveness can vary. Targeted therapies, such as Tazemetostat, have also been developed for unresectable or metastatic epithelioid sarcoma, offering additional options.
Long-Term Outlook
The long-term outlook for epithelioid sarcoma varies based on tumor size, location, and completeness of surgical removal. Distal locations (e.g., hands, feet) and smaller tumor sizes are associated with a more favorable prognosis. Despite initial treatment, epithelioid sarcoma has a tendency for local recurrence and can spread to regional lymph nodes or distant organs, most commonly the lungs.
Regular follow-up and surveillance are important for long-term management to monitor for recurrence. This may involve physical examinations and imaging scans for at least 5 to 10 years, as late recurrences can occur. The goal of long-term care is to detect and manage new disease activity promptly, maintaining the best possible quality of life.