MDM2 and neoplasm: Further immunohistochemical studies showed the tumor cells were positive for CD21, CD23, somatostatin receptor 2A, and MDM2 (Fig. 2c-e), while negative for HHV8, PAX8, PAX2 AE1/AE3, CK7, MelanA, S100, CD68, SMA, TdT, desmin, and podoplanin (Suppl.