PAX7 and alveolar rhabdomyosarcoma: For instance, the diagnosis of alveolar rhabdomyosarcoma (ARMS) is typically based on histopathological features, IHC results (most importantly desmin, MyoD1, and myogenin), and molecular results (RT-PCR for PAX3/PAX7–FOXO1 or FISH for PAX3/FOXO1 rearrangement).