Detection of human herpes virus type 8 DNA sequences as a valuable aid in the differential diagnosis of Kaposi's sarcoma.

The occurrence of human herpes virus type 8 (HHV-8) DNA sequences was evaluated by polymerase chain reaction in 36 cases of cutaneous Kaposi's sarcoma (KS) (classic and associated with the acquired immunodeficiency syndrome) and in 88 pathologic entities that can histologically mimic KS, such as reactive and neoplastic vascular processes and lesions featuring focal or extensive spindle cell pattern. A positive reaction was detected in 16 (70%) of 23 samples of classic KS and 10 (77%) of 13 KS cases related to the acquired immunodeficiency syndrome. In particular, 4 (50%) of 8 samples in the patch stage were found to be positive, whereas in the plaque and nodular stages, HHV-8 DNA sequences were observed in 8 (67%) of 12 and 14 (87%) of 16 cases, respectively. KS cases that had yielded previous negative results were found to be positive for HHV-8 on nested polymerase chain reaction, except two cases of classic KS in the patch stage (6% of the total number of KS, 25% of cases in the patch stage). Reactive and neoplastic vascular processes and cutaneous lesions with a spindle cell component were consistently negative. HHV-8 detection by polymerase chain reaction can represent a valuable method for diagnosing KS, particularly in small skin biopsy samples that might show histologic overlap with non-KS lesions. In early patch stage lesions, however, the diagnostic value of the method is hampered by the occurrence of cases in which HHV-8 sequences are still undetectable.