Detection of cytomegalovirus DNA in classic and epidemic Kaposi's sarcoma by in situ hybridization.

Several lines of evidence have suggested an etiologic association of cytomegalovirus (CMV) with Kaposi's sarcoma. This contention is supported by a pathoepidemiologic survey of 54 cases of acquired immunodeficiency syndrome (AIDS) at our own institution. Of the 27 patients with documented Kaposi's sarcoma, 24 (89%) showed histologic evidence of CMV infection (cytomegalic cells with viral inclusions), whereas only 9 (33%) of the patients with AIDS without Kaposi's sarcoma showed hallmarks of CMV infection. In an attempt to address this question further, we have searched for the presence of CMV nucleic acid sequences in a series of 25 patients with AIDS and Kaposi's sarcoma, using the technique of in situ DNA hybridization. The reliability of the in situ technique is demonstrated, and the technique is shown to be more sensitive than the detection of viral inclusions within Kaposi's sarcoma lesions by routine light microscopy. However, only 20% of our cases showed evidence of CMV involvement, and the CMV-positive cells within the affected Kaposi's sarcoma lesions were few and sparsely distributed. In addition, a companion series of 6 elderly patients with "classic" Kaposi's sarcoma showed no evidence of CMV infection by either conventional microscopy or in situ hybridization. These results do not support the notion of a strong association between Kaposi's sarcoma and CMV, unless the CMV sequences are present at a copy number too low for detection by these methods. The implications of these findings in light of current theories of CMV oncogenesis are discussed.