PTEN and sarcoma: Many mechanisms contribute to IGF1R overexpression in sarcomas [24] such as receptor upregulation or overexpression of ligands driven by multiple mechanisms like fusion genes (PAX3-FKHR; EWS-WT1; EWS-FLI1), loss of imprinting (LOI) of IGF2, or loss of tumor suppressor genes (WT1, PTEN, p53).