Recent studies has shown that the ASPL-TFE3 fusion transcript can be identified by RT-PCR analysis and TFE3 gene rearragement can be detected using a dual-color, break apart FISH assay in paraffin-embedded tissue, both can be uesd as powerful tools for diagnosis of ASPS [12, 16, 17], in addition, the resultant fusion protein can be detected by IHC with an antibody directed to the carboxy terminal portion of TFE3 with high sensitivity and specificity [18]; all the three tools were used in the current case to confirm the diagnosis of ASPS in the lung. Here, TFE3 is linked to alveolar soft part sarcoma.