ASPS is characterized by a specific chromosomal alteration, der (17)t(X:17)(p11:q25), resulting in the fusion of the TFE3 transcription factor gene (from Xp11) with alveolar soft part sarcoma critical region 1 (ASPSCR1), also known as alveolar soft part sarcoma locus at 17q25 (6,33). The gene discussed is ASPSCR1; the disease is alveolar soft part sarcoma.