The overall sensitivity of TFE3 immunohistochemistry to detect TFE3‐rearranged neoplasms was 85% in laboratory A, and 70% in laboratory B. The difference in detection rate could be attributed to different fixation or processing techniques used by each laboratory, yet the presence or absence of immunohistochemical reactivity was not sufficient alone to confirm the diagnosis of ASPS since the specificities of IHC in lab A and lab B were 57% and 95% respectively. The gene discussed is TFE3; the disease is alveolar soft part sarcoma.