CD99 and neoplasm: Additionally, the tumor was negative for most immunohistochemical markers (CKAE1/AE3, p63, CD23, CD21, MUC4, NUT, CDK4, Pan-TRK, STAT6, SS18, MDM2, Desmin, S100, ERG, TLE1, Fli) and showed only weak and most probably unspecific expression of CD99, CD56, and CD34.