In vitro study of the cell populations in two cases of Kaposi's sarcoma.

Despite numerous studies, the histogenesis of Kaposi's sarcoma remains unclear. In connection with the culture of two Kaposi's sarcomas, the morphological, ultrastructural, and immunological properties of the various cell types observed are discussed. Cloning in agar, loss of contact inhibition, and karyotyping were used to determine which cells had undergone malignant transformation. Findings for both cases revealed that endothelial cells had undergone neoplastic transformation. Fibroblastic cell lines were isolated from both sarcoma fragments; although their growth characteristics distinguished them from normal fibroblasts (increased growth and possibility of culture in soft agar), cytogenetic investigations on both lines confirmed that they were genetically normal, and occurred along with malignant cells as a accessory compartment within lesions. Endothelial cells appear to be the sole origin of Kaposi's sarcoma, and may release factors which alter fibroblastic growth.