STAT3 and neoplasm: Combined with germline PTPRD mutations, among which a p.W775* nonsense variant, that were observed in Ewing sarcoma cases (Jiang et al., 2013)—a tumor type often displaying elevated STAT3 activity – this lends support for an important role of RPTPδ in dephosphorylation of STAT3, downstream of insulin growth factor receptor (IGF-1R).