Increased embryonal rhabdomyosarcoma (eRMS) incidence and decreased age of onset in p53-deficient mdx mice. Mice defective in expression of p53 (Trp53), mice defective in the expression of dystrophin (mdx), and mice partially or completely deficient in p53 and dystrophin (Trp53+/− mdx or Trp53−/− mdx) were assessed for development of rhabdomyosarcoma at different ages. All muscle-derived RMS identified were embryonal RMS (eRMS). Data are reported as a percentage of the total animals for each individual genotype. n = 450 Trp53+/+ (wild-type), 26 Trp53+/−, 22 Trp53−/−, 360 Trp53+/+ mdx, 56 Trp53+/− mdx and 22 Trp53−/− mdx animals.