TP53 and osteosarcoma: We also define the pathogenicity of three TP53 mutations: (1) a TP53C176F variant found in ERMS patients (Chen, 2013; Seki et al., 2015; Shern et al., 2014); (2) a TP53P153Δ variant of unknown significance, found in a teenager with an aggressive osteosarcoma at our clinic; and (3) a p53Y220C mutant that is structurally related to p53P153Δ and may share some aspects of its function.