Fig. 6.

Immunohistochemical evidence of pericyte origin of renal angiomyolipomas. A: the endothelial cell marker CD31 in an epithelioid angiomyolipoma from a patient with TSC (×400 magnification). B: CD31 staining in a spindle cell predominant angiomyolipoma from a patient with TSC (×400 magnification). C: immunohistochemical staining of an angiomyolipoma for PDGF receptor (PDGFR)-β. The section revealed a tangential cut through a blood vessel wall such that the center is vascular smooth muscle (VSM), which was not stained, but the surrounding pericytes stained strongly positive for PDGFR-β. Angiomyolipoma surrounding the vessel also stained positive for PDGFR-β (×400 magnification). D: immunohistochemical staining for VEGFR2. This section was slightly deeper and revealed the vessel lumen. VSM cells did not stain, but the surrounding endothelial, pericyte, and angiomyolipoma cells all exhibited robust staining for VEGFR2 (×400 magnification). E: immunohistochemical staining of an angiomyolipoma for desmin. The section revealed a tangential cut through a blood vessel wall with a similar staining pattern as that of PDGFR-β. F: immunohistochemical staining of an angiomyolipoma for α-smooth muscle actin (α-SMA). VSM and the surrounding pericytes/tumor areas were strongly positive. Four separate TSC-associated angiomyolipomas were analyzed.