The most aggressive ARMS is dominated by a chromosomal translocation t(2;13)(q35;q14) that juxtaposes the DNA binding domain of the PAX3 gene in a frame with the activation domain of the FOXO1 gene, giving rise to a Pax3-Foxo1 chimeric transcription factor that is found in 70% of ARMS cases and is considered a predictor of poor prognosis [92,93]. The gene discussed is PAX3; the disease is alveolar rhabdomyosarcoma.