There is morphologic overlap between ASPS and other tumors with similar presentations, and as discussed above, other promising stain-based biomarkers for ASPS such as TFE3 and cathepsin K have limitations (with unfortunately low specificity when comparing entities commonly considered along with ASPS), leading to the need for a more specific biomarker. The gene discussed is TFE3; the disease is alveolar soft part sarcoma.