Alveolar soft-part sarcomas
Alveolar soft-part sarcoma (ASPS) is a rare and slow-growing malignant tumor that primarily develops in deep soft tissues and muscles, particularly in areas like the thighs, buttocks, and occasionally in the arms, chest, or abdomen. It is characterized by tumor cells that resemble the air sacs of the lungs, known as alveoli. Although the exact cause of ASPS remains unclear, it is associated with a genetic mutation involving the ASPL gene. The tumor is nonhereditary, and no specific risk factors have been identified.
ASPS comprises about 1% of all soft-tissue sarcomas, with approximately 13,590 new cases expected in the U.S. in 2024. Symptoms often include a soft, painless lump, soreness, and reduced mobility, which can lead to late diagnosis as the tumor grows. Diagnosis typically involves imaging studies and a biopsy. Treatment primarily focuses on surgical removal of the tumor, with radiation therapy sometimes used, although chemotherapy has limited effectiveness.
The prognosis for ASPS can vary; localized tumors have a five-year survival rate of around 81%, while metastasized cases exhibit poorer outcomes. Notably, children diagnosed with ASPS tend to have better prognosis due to generally smaller and more localized tumors. Given the potential for recurrence, long-term follow-up is essential for patients.
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Subject Terms
Alveolar soft-part sarcomas
ALSO KNOWN AS: Nonrhabdomyosarcoma soft-tissue sarcomas, ASPS
RELATED CONDITIONS: Soft-tissue sarcomas
DEFINITION:DEFINITION: Alveolar soft-part sarcoma is a slow-growing, malignant tumor that develops in deep soft tissues and muscles, most often in the thighs and buttocks. It is also found in the arm, chest, bladder, abdomen, and in children, the head and neck. Its name is derived from how its tumor cells are clustered, resembling alveoli or the air sacs of the lungs.
Risk factors: No risk factors are known, and alveolar soft-part sarcoma is nonhereditary.
Etiology and the disease process: The etiology of the disease is murky. Early development of alveolar soft-part sarcoma appears to be linked to a genetic mutation involving the separation of the ASPL gene from chromosome 17 and its attachment to the X chromosome. A wealth of blood vessels allows tumor cells to enter the bloodstream and spread to other areas, usually the lungs and brain. Childhood alveolar soft-part sarcoma appears to have a different and generally less aggressive biology.
Incidence: Alveolar soft-part sarcoma is rare, comprising only 1 percent of all soft-tissue sarcomas. According to statistics from the American Cancer Society, in 2024, 13,590 new soft-tissue sarcoma cases are expected to be diagnosed; 7,770 will be in males and 5,890 in females. There will be an expected 5,200 mortalities. The younger the sarcoma patient is at the time of their diagnosis, the more likely the same person will have a relapse later in life. The median age of soft tissue sarcoma patients will be 56.
Symptoms: Common symptoms include a soft, painless lump, soreness, reduced range of motion, and numbness. Because alveolar soft-part sarcoma grows slowly in deep, elastic tissues, patients often do not notice symptoms until the cancer has advanced or has spread.
Screening and staging: Diagnostic procedures include laboratory tests and imaging studies such as computed tomography (CT) scans, positron emission tomography (PET) scans, magnetic resonance imaging (MRI), and bone scans. A biopsy is required, however, to confirm alveolar soft-part sarcoma. Tumors are staged based on size, grade, and degree of spread:
- Stage I: Low grade, with little potential for spreading
- Stages II and III: High grade, with increased potential for spreading
- Stage IV: Metastasis to distant organs
Other criteria are typically used for staging pediatric alveolar soft-part sarcoma.
Treatment and therapy: Surgical removal of the tumor and surrounding tissue is the primary treatment. Occasionally, amputation is required. Radiation therapy may be used to shrink the tumor and kill any remaining cells. Radiation therapy is used in children only if surgery alone is ineffective. Chemotherapy is not generally beneficial. The American Society of Clinical Oncology reported in 2013 that other therapies, such as targeted gene therapy and immunotherapy, were under study. More than a decade later, in 2024, results of immunotherapy treatments showed limited positive results. Outcomes tended to show slightly better outcomes when combined with other treatment strategies.
Prognosis, prevention, and outcomes: In 2024, the five-year survival rate for patients with localized tumors is around 81 percent, but it will be far less if the disease has metastasized. Long-term survival is nonetheless possible even with spread because alveolar soft tissue sarcoma grows slowly. The prognosis for children is considerably better, as their tumors are generally smaller and localized. Alveolar soft-part sarcoma can recur more than ten years after initial diagnosis, so long-term follow-up is recommended.
Bibliography
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