CD44 and Ewing sarcoma: Importantly, heparan sulfate proteoglycans play an essential role in differentiation and migration of both neural crest and mesenchymal cells – both of them are considered as potential cell of origin of Ewing sarcoma (Henderson and Copp, 1997; Long and Huttner, 2019; Papy-Garcia and Albanese, 2017; Yaylaci et al., 2016).