ASPS arises mainly in children and young adults and can migrate (metastasize) into other parts of the body, typically the lungs and the brain.

The resultant fusion protein ASPL–TFE3 is a rogue transcription factor that is the driver of aberrant cellular behavior including uncontrolled cell division and enhanced angiogenesis.

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.

ASPS' histomorphologic features include an alveolar-like pattern at low magnification and the presence of large cells with abundant eosinophilic cytoplasm and eccentric nuclei.

Such low numbers of occurrence seriously impede the search for a cure by making it hard to gather any meaningful statistics about the disease.