No abstract

Eleven biopsy specimens of Kaposi's sarcoma (KS) removed from the skin and oral mucosa were examined immunohistochemically with monoclonal antibodies PAL‐E and EN‐4, specific for human vascular endothelial cells, and with LN‐3 monoclonal antibody reactive with immune‐associated (la) antigens in the HLA‐DR locus. The early lesions of KS, corresponding to the patch phase, contained hyperplastic venules and an increased number of lymphatic capillaries. The lymphatic capillary endothelium was reactive with EN‐4, whereas, PAL‐E reacted only with blood vessel endothelial cells. The spindle cells, like lymphatic endothelial cells, were non‐reactive with PAL‐E but showed positive reaction with EN‐4 antibodies. The observed morphologic pattern of vasculogenesis and the demonstrated immune‐reactivity in KS support an origin from the venul‐lymphatic junction. This is an aberrant pattern but reminiscent of normal embryonal lymphatic channel development. The lymphatic capillaries and vascular slits were nonreactive with LN‐3 antibody, but it was positive on cell membranes in a number of spindle cells, suggesting the focal expression of la‐anitgens.