Kaposi's sarcoma: ultrastructural study and immunoperoxidase localization of factor VIII-related antigen

ABSTRACT

Fifteen patients with Kaposi's sarcoma were studied. Nine patients had early cutaneous plaques and six patients had locally extensive nodular lesions with lymph node affection in two patients. Satisfactory electron micrographs after initial 10% formalin fixation were obtained in two cases. Factor VIII-related antigen localization was studied by immunoperoxidase stain in eight cases with available paraffin blocks. Ultrastructurally, the tumor contained variable mixture of cells including endothelial cells, pericytes, fibroblasts and myofibroblasts. Immunoperoxidase staining for factor VIII-related antigen was positive in all the eight cases with positive cytoplasmic staining in the endothelial cells lining of the well formed blood vessels and some proliferating spindle cells indicating their vascular [endothelial] derivation. The histologic features which help in the diagnosis of Kaposi's sarcoma from other histologic entities were reviewed. The presence of abnormally shaped vessels with jagged outline was the most helpful single criterion to diagnose early lesions