Major basement membrane components in Kaposi's sarcoma, angiosarcoma and benign vascular neogenesis

Recent cell biologic studies have emphasized the importance of the basement membrane (BM) and its molecular components in angiogenesis. We immunostained 60 angioproliferative lesions (angiosarcoma, sclerosing hemangioma of skin, pyogenic granuloma, capillary hemangioma, lymphangioma, glomangioma and granulation tissue) and 23 cases of Kaposi's sarcoma (KS) for the major macromolecular components laminin, collagen type IV, fibronectin and heparan sulfate proteoglycan (HSPG). Normal structures served as aggregate controls in each group, and semiquantitative scoring reflected the degree of consistency of staining about blood and lymphatic endothelium and vascular sheath (pericyte/smooth muscle) within and peripheral to each lesion. Benign and reactive vasoproliferations consistently maintained immunoreactivity for each BM component around endothelium and sheath components of blood vessels. Angiosarcoma showed from 20 to more than 60% less consistent immunoreactivity by comparison, although the score variances were greater than for non‐malignant lesions. Staining about blood vessel endothelium was both strong and consistent among histologic stages in KS with the exception of HSPG, which was weakly immunoreactive in all stages. Marked selective HSPG loss was characteristic only of KS and normal lymphendothelium, and in the light of evidence for a role for HSPG in the assembly and maintenance of BM, suggests that reduced HSPG may be responsible for the loss of ultrastructural integrity of perivascular BM in both.