To determine whether a KSHV-linked mechanism of PDGF upregulation was responsible for PDGFRA phosphorylation in mECK36 tumors and AIDS-KS lesions, we carried out an immunohistochemical analysis for phospho-PDGFRA, KSHV-LANA (latency-associated nuclear antigen, a marker of KSHV infection), PDGFA and PDGFB. This evidence concerns the gene PDGFB and Kaposi's sarcoma.