Alveolar soft-part sarcoma (ASPS)

Alveolar soft-part sarcoma, also known as ASPS or alveolar sarcoma of soft parts, is an extremely rare type of soft tissue sarcoma. ASPS diagnoses make up less than 1 percent of soft tissue sarcomas, with just 80 cases diagnosed in the U.S. each year, on average.

This type of cancerous tumor mainly occurs in teens and young adults ages 15 to 35. ASPS cancers can develop in many areas of the body, but in teens, they most often occur in the head and neck. In young adults, they tend to form in the thighs or buttocks.

Most cases of ASPS grow in unusual ways. Early-stage, small tumors create a network of blood vessels that allows them to metastasize (spread) early on. In about two-thirds of cases, ASPS has spread—often to the lungs, bones, and brain—by the time the disease is diagnosed. Unlike many other cancers, metastatic tumors from ASPS grow slowly.

The Sarcoma Program at Penn Medicine’s Abramson Cancer Center has one of the most experienced teams in the nation when it comes to treating ASPS. Our surgeons can often save limbs affected by tumors, while other specialists can provide new drug therapies.

Our team also works closely with the Sarcoma Program at the Children’s Hospital of Philadelphia when appropriate. Some of our surgeons even work at both Penn and CHOP, providing easy access between sarcoma programs and a seamless transition to adult care.

Symptoms of ASPS vary depending on the stage of the cancer. Some ASPS tumors may cause a lump or swelling, but these changes are often painless. The tumor may not cause notable symptoms until it has grown larger and begun pushing on nerves or muscles. At that point, you may experience:

• Reduced range of motion in a joint
• Limping
• Pain or soreness in the affected area

You may also experience symptoms from metastatic ASPS tumors depending on the location of the additional tumor(s).

Researchers have not yet discovered why some people develop ASPS, in large part because it is so rare. However, they do understand some of the changes that drive the formation of the cancer.

Cells in all ASPS tumors experience changes to chromosomes, the structures made of DNA that contain genes. With ASPS, chromosomes break apart and then reform, moving a pair of specific genes to different spots. This relocation seems to cause the cells to act differently. Researchers do not know why this chromosomal swap happens with ASPS.

Unlike some other soft tissue sarcomas, there is no evidence that past radiation therapy or chemical exposure have connections to ASPS. The cancer also does not run in families—the gene changes are not passed down to children.

There is currently no known way to lower your risk for developing ASPS.

Diagnosing ASPS while it is still in its early stages is often challenging because smaller tumors typically show no symptoms.

At Penn Medicine, an evaluation for ASPS starts with our team asking about your symptoms and examining any lumps or swelling. We will also recommend imaging tests such as magnetic resonance imaging (MRI) to determine the tumor’s size and precise location. A computed tomography (CT) scan can determine whether the sarcoma has spread and, if so, to which parts of the body.

To confirm a diagnosis, specialized radiologists may perform an image-guided needle biopsy. By removing a small sample of tumor tissue, our specialized cancer pathologists can study it under a microscope and run lab tests, including looking for genetic changes.

Together, the exam, scans, and biopsy results help our team stage, or further categorize, the cancer to guide treatment planning.

While doctors can treat ASPS, prognosis depends on:

• Tumor size and location
• Patient age and overall health
• Whether cancer has spread and where it has spread to

Treatment for all sarcoma types—including ASPS—focuses on completely removing the initial tumor. For all sarcoma surgeries, the most effective approach requires taking the tumor out in one piece, an approach our surgeons specialize in. Doctors on our team may also recommend radiation therapy before the operation to reduce the chance that the sarcoma returns.

ASPS does not respond to current chemotherapy drugs. This presents a challenge for ASPS tumors that have spread and cannot be removed with surgery. For these tumors, our team can turn to emerging therapies such as targeted therapy and immunotherapy. Targeted therapy works against cellular processes that cancers need to grow. Immunotherapy harnesses the body’s immune system to fight cancer. Sarcoma clinical trials for ASPS may combine both approaches.

Even with successful initial treatment, ASPS may return in another location. Watching for that possibility requires ongoing checkups. At Penn Medicine, our team continues to work to improve ASPS treatment and develop further options, including limb-sparing surgeries for ASPS in the arms or legs.