Angiogenesis and lymphangiogenesis in sporadic hepatic angiomyolipoma

Angiogenesis and lymphangiogenesis are critical processes for tumor growth, invasion, and metastasis. The present study aimed to investigate the distribution and clinical significance of angiogenesis and lymphangiogenesis in hepatic angiomyolipoma (AML). We performed immunohistochemical staining for endothelial cell markers (CD34 and podoplanin) on 80 cases of sporadic hepatic AMLs. Microvessel density (MVD) and lymphatic vessel density (LVD) were determined in intratumoral and peritumoral regions and adjacent non-tumorous liver tissues. All hepatic AMLs showed positive staining for CD34 and podoplanin. Intratumoral and peritumoral MVDs and LVDs were significantly higher than those in adjacent liver tissues (P<0.001). No statistical difference in both MVD and LVD was found between intratumoral and peritumoral areas. Large tumors (>5cm) had a significantly increased MVD and LVD as compared with smaller tumors. A significant positive correlation was found between average LVDs and MVDs (r=0.567, P<0.001), and LVDs were a relatively lower event as compared with MVDs. Double immunostaining revealed that no neoplastic cells positive for HMB-45, an antibody reacting with melanosome-associated antigen, were concurrently immunoreactive for endothelial cell markers. In conclusion, intratumoral and peritumoral angiogenesis and lymphangiogenesis commonly occur in hepatic AMLs, thus representing potential therapeutic targets for this disease.