CD99 and neoplasm: Accordingly, several immunomarkers, including NK2 homeobox 2 (NKX2.2) and cluster of differentiation 99 (CD99) for Ewing sarcoma (ES)4,5, desmin and myogenin for rhabdomyosarcoma5, and SWI/SNF-related matrix-associated actin-dependent regulator of chromatin (SMARC) subfamily B member 1 (SMARCB1) for malignant rhabdoid tumor, can be used to distinguish tumor subtypes6.