CD99 and B-cell chronic lymphocytic leukemia: Other markers such as Caveolin-1, NK2 homeobox 2 (Nkx-2.2), or combinations of immunohistochemical markers such as B-cell CLL/lymphoma 11B (BCL11B) and Golgi glycoprotein 1 (GLG1) have been proposed to support diagnosis of EwS, especially in cases negative for CD99 expression, but these require validation in prospective studies [71,73,74] (Figure 3).