Histological analysis of Pax3:Foxo1a,p53,Rb1 tumors. Histological analysis of Pax3:Foxo1a,p53,Rb1 tumors demonstrate small round blue cells with positive myogenin and desmin staining, consistent with aRMS (tumor 1 and tumor 2). However, some tumors showed highly anaplastic morphology (tumor 3) and were diagnosed as pleomorphic RMS. The Pax3:Foxo1a transcript level by qRT-PCR for the right tumor was nearly the same as for the middle tumor (data not shown). Scale bar: 40 μm. H&E, hematoxylin and eosin.