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. The gene discussed is PDGFRA; the disease is Kaposi's sarcoma.