PAX3 gene is a member of the paired box (PAX) family of transcription factors. Members of the PAX family typically contain a paired box domain and a paired-type homeodomain. These genes play critical roles during fetal development. Mutations in paired box gene 3 are associated with Waardenburg syndrome, craniofacial-deafness-hand syndrome, and alveolar rhabdomyosarcoma. Translocations involving the FOXO1 (forkhead box O1) gene at 13q14.1 and either the PAX3 (paired box 3) gene at 2q36.1 or the PAX7 (paired box 7) gene at 1p36.1 are seen frequently in cases of alveolar rhabdomyosarcoma. Rhabdomyosarcoma is the most common soft-tissue sarcoma seen in children and younger adults with two major histological subtypes: alveolar rhabdomyosarcoma (ARMS) and embryonal rhabdomyosarcoma (ERMS). FOXO1 rearrangements are recognised recurrent abnormalities seen in ARMS, but not seen in ERMS. Most (75%) ARMS cases display recurrent chromosomal translocation that fuses two transcription factor-encoding genes together; the PAX3 gene (in a minority of cases the PAX7 gene) and the FOXO1 gene.