Absence of Kaposi's sarcoma-associated herpesvirus DNA from PBL. (PCR, 6% polyacrylamide gel, staining with ethidium bromide). Case no. 1, tumor of patient no. 12; case no. 2, tumor of patient no. 15; case no. 3, tumor of patient no. 9; negative control, DNA extracted from a tonsil; positive control, Kaposi's sarcoma.