CD99 and Ewing sarcoma: Other markers such as neuron-specific enolase (NSE), S-100 protein, CD57, neurofilaments, cytokeratin, desmin, caveolin-1, NK2 homeobox 2 (Nkx-2.2) or immunohistochemical markers such as B-cell CLL/lymphoma 11B (BCL11B) and Golgi glycoprotein 1 (GLG1) have been investigated in Ewing sarcoma diagnosis, especially in cases with negative CD99 detection [22,23,24,25,26,27,28].