With regard to embryonal rhabdomyosarcomas in the pediatric setting, these can be distinguished from IMTs by (a) exhibiting greater cellularity and increased numbers of atypical mitotic figures, (b) the presence of rhabdomyoblasts, a uniform population of small hyperchromatic cells, (c) a "cambium layer" (small malignant cells characteristically grouped beneath the epithelium) and (d) positive myogenin (Myf4) and MyoD1 immunostainings [5,11,19,20]. The gene discussed is MYOG; the disease is rhabdomyosarcoma.