Alveolar soft part sarcoma

Synonyms

2

Overview

Alveolar soft part sarcoma (ASPS) is a rare slow-growing malignant connective tissue tumor. It is a type of Soft tissue sarcoma that hat begins in the soft tissues of your body. 

ASPA (tumors) occur most frequently in the arms and legs. The deep soft tissue of the thigh, tongue, eye orbit, and head and neck regions are also common sites. Metastasis is frequent with lung and brain being most common metastatic sites. Symptoms are determined by the location, size and stage of the tumor.

In ASPS it  indicates that this cancer initially arises from tissue of embryonic mesenchymal origin. (The fertilized egg divides and redivides forming a sphere. Early in embryogenesis, dimples appear in the poles of the sphere and burrow through the sphere forming an inner passage that will ultimately form the gut. Malignancies arising from cells that were originally part of the outer layer of the sphere and those that were part of the embryonic tunnel are termed carcinomas; malignancies arising from the cells between the outer layer and the inner burrow are termed sarcomas.) Typically, ASPS arises in muscles and deep soft tissue of the thigh or the leg (lower extremities), but can also appear in the upper extremities (hands, neck, and head). While ASPS is a soft tissue sarcoma, it can also spread and grow inside the bones.

The term alveolar comes from the microscopic pattern, visible during the analysis of slides of ASPS under the microscope in histopathology. The tumor cells seem to be arranged in the same pattern as the cells of the small air sacks (alveoli) in the lungs. However, this is just a structural similarity. ASPS was first described and characterized in 1952.

Symptoms

  • Painless mass
  • Asymptomatic
  • Proptosis
  • Eyelid swelling

Causes

Chromosomal analysis of ASPS shows the breaking and joining of two chromosomes in the tumor cells. A piece of chromosome X breaks and is joined to chromosome 17. This translocation creates a fusion between two genes named ASPL and TFE3, which results in the formation of an aberrant protein (termed fusion protein) that is not found in normal cells. Two sorts of fusions between chromosome X and chromosome 17 are found in different ASPS tumors: Type one, and type two. Dr. Ladanyi at Memorial Sloan-Kettering Cancer Center, in New York, has pioneered this work.

Diagnosis

ASPS may exist in the patient’s body for a long time before being diagnosed. It can grow large and push aside surrounding tissues for a long time before causing any discomfort. Therefore, ASPS symptoms may either be a painless swelling, or a soreness caused by compressed nerves or muscles, affecting the range of motion in the area.

Pathology:
The definitive diagnosis of ASPS is based on its appearance under the microscope, i.e. its histomorphology, and presence of the characteristic chromosomal translocation.

ASPS' histomorphologic features include an alveolar-like pattern at low magnification and the presence of large cells with abundant eosinophilic cytoplasm and eccentric nuclei. Calcifications are commonly present, as may be seen with slow growing neoplasms.

Prognosis

Although ASPS displays a relatively indolent course, the ultimate prognosis is poor and is often characterized by late metastases.

Treatment

The general treatment options for soft tissue sarcoma will depend on the size, type and location of your tumor.

Surgery:

Surgery is a common treatment for soft tissue sarcoma. Surgery generally involves removing the cancer and some healthy tissue surrounding it.

When soft tissue sarcoma affects the arms and legs, it may be necessary to amputate the affected arm or leg. Doctors try their best to avoid amputation. One option to achieve this may be using chemotherapy and radiation to shrink the tumor before surgery, which increases the likelihood that an amputation will be unnecessary.

When soft tissue sarcoma spreads to another area of the body, it may be possible to remove the other tumor with surgery, as well.

Radiation therapy:

Radiation therapy involves treating cancer with high-powered beams of energy, such as X-rays or protons.

Your doctor may suggest using radiation therapy before surgery to shrink a tumor to make it easier to remove with surgery. Radiation is also used after surgery to kill any cancer cells that remain.

Chemotherapy and radiation may be combined.

Chemotherapy:

Chemotherapy is a drug treatment that uses chemicals to kill cancer cells. Chemotherapy can be administered by pill, through a vein (intravenously), or both methods may be used.

Some forms of soft tissue sarcoma respond better to chemotherapy than do others. For instance, chemotherapy is often used to treat rhabdomyosarcoma.

Targeted drug treatment:

Targeted drugs block specific abnormal signals present in sarcoma cells that allow them to grow.

Targeted drugs used to treat one type of sarcoma called gastrointestinal stromal tumor include:

  • Imatinib (Gleevec)
  • Sunitinib (Sutent)
  • Regorafenib (Stigvara)
  • Pazopanib (Votrient)
  • Many new targeted drugs are being studied

Resources

  • Mayo Clinic
  • Genetics Home Reference
  • NIH