Fine structure and origin of Kaposi's sarcoma.

Tumour cells in Kaposi's sarcoma with visceral involvement were studied by fine structural analysis. In the cytoplasm of these cells rod-shaped tubulated bodies resembling Weibel-Palade granules could be demonstrated. This finding and the occurrence of a basement membrane around the tumour cells characterize Kaposi cells as endothelial cells of blood vessels which may originate from undifferentiated vasoformative cells of the adventitia.