Ultrastructure of Kaposi's sarcoma in acquired immune deficiency syndrome (AIDS).

We used electron microscopy to examine the ultrastructural morphology of Kaposi's sarcoma (KS) of the oral mucosa in patients with acquired immune deficiency syndrome (AIDS). The tumors manifested endothelial vascular proliferation and neoplastic spindle cell formations. The endothelial tumor cells contained several multivesicular bodies and a large number of tubuloreticular structures within the endoplasmic reticulum. Ultrastructural changes in the other cytoplasmic organelles included defective cell junctions that seemed to facilitate the migration and extravasation of erythrocytes through endothelial gaps, after which erythrophagocytosis occurred. Tumor cells contained viral particles which were 100-120 nm in diameter and contained dense cylindrical cores. We believe that this is the first time these particles have been identified in KS cells of the oral mucosa in patients with AIDS. These viral particles are also ultrastructurally identical to the human T-cell lymphotropic retroviruses subgroup HTLV-III. Our observations are discussed in the light of recent immunological findings.