Ultrastructural study of Kaposi's sarcoma.

An electron microscopic (EM) study of 25 Kaposi's sarcomas (KS) (24 cutaneous lesions, 1 lymphnodal) from 23 patients, mainly sporadic in type, has enabled us to study both the spindle and endothelial cells seen by light microscopy (LM) with the conclusion that they have both a fibroblastic-like EM aspect. Both cell types manifested a spindle shape with oval and occasionally notched nuclei and a reticular pattern of nucleoli. The cytoplasm was characterized by numerous rough endoplasmic reticulum cisternae with few other organelles. The plasma membranes consistently lacked an external or basal membrane and failed to show true cell junctions. In cells delimiting erythrocytes containing spaces it was never possible to document Weibel-Palade (W.-P.) bodies or plasmalemmal vesicles. Unusual findings such as ferritin loaded phagosomes, microtubular reticular structures (MTRS), intracisternal crystalline inclusions (ICCI), multivesicular bodies (MVB), acanthosomic vesicles (AV) and test-tube inclusions or ring-shaped forms (TTI/RSF) were occasionally seen in both sporadic and epidemic KS. The authors discuss the non specific nature of these latter findings.