WWTR1 and alveolar rhabdomyosarcoma: WWTR1 is a downstream effector of the Hippo signal transduction pathway, a major player in different types of sarcoma, including ARMS [37,38,39,40], and in epithelioid hemangioendothelioma, WWTR1-CAMTA1 has been identified as a disease-defining gene fusion [41,42,43,44].