In cases with a CD99 IRS greater than 8 (meaning strong membranous staining intensity in at least 60% of tumor cells), the diagnosis of EwS should be either confirmed by molecular pathology approaches that can reliably detect FET-ETS fusions such as qRT-PCR or RNA-seq, or by immunohistochemical staining for the auxiliary markers BCL11B and GLG1. The gene discussed is CD99; the disease is neoplasm.