[Ultrastructural morphology of Kaposi sarcoma of the head and neck in acquired immunodeficiency syndrome (AIDS)].

The ultrastructural morphology of Kaposi's sarcoma in the skin and mucous membranes of the head and neck regions of patients with acquired immune deficiency syndrome (AIDS) was examined electron microscopically. It was found that the tumour consisted of neoplastic spindle cell aggregates, vascular endothelial cell proliferations and an inflammatory infiltrate of lymphocytes and plasma cells. Not only abnormal blood vessel endothelial proliferations, but also irregular lymphatic luminal formations were observed. Moreover, tubuloreticular structures, helical polysomes, giant multivesicular bodies as well as test-tube and ring-shaped forms were found in the tumour cells. Erythrophagocytosis in various stages including ultimately the production of siderosomes was also seen. There was also some mitotic activity in the tumour cells. Retroviruses of 100-120 nm, morphologically identical to HTLV-III, were budding from the plasma membrane of some of the Kaposi's sarcoma cells. As these retroviruses are able to replicate in Kaposi's sarcoma cells without having a clear relation to the tumourogenesis, the characterisation as well as quantification of the virus-producing cells may well prove highly relevant.