Distribution of basement membrane-associated heparan sulfate proteoglycan in idiopathic and AIDS-associated Kaposi's sarcoma.

In the present study we analyzed the immunohistochemical distribution of different major basement membrane (BM) components with special emphasis on the BM-associated heparan sulfate proteoglycan (HSPG) in early and late stages of Kaposi's sarcoma (KS), both of idiopathic and AIDS-associated origin. In early KS all BM components tested were found surrounding the small clefts of tumour vessels. Heparan sulfate proteoglycan showed the weakest and often fragmented pattern of staining. In the late, nodular sarcomatous form of KS individual tumour cells were surrounded by a BM composed of collagen IV, laminin and fibronectin, while heparan sulfate proteoglycan was not detectable in most cases. Neither between idiopathic and AIDS-associated KS nor between cutaneous and visceral lesions were significant differences in the staining pattern. Our findings of a rather selective expression of various BM-components and the known distribution in normal blood and lymphatic capillaries raises the hypothesis that KS-cells may be derived from cells of lymphaticovenous differentiation.