['Primary effusion lymphoma (PEL) associates with HHV-8 infection, preferentially develops in immunodeficient patients and grows in the serous body cavities. PEL derives from post-germinal center, pre-terminally differentiated B-cells. The pathogenesis of PEL is unclear and the sole identified genetic lesions are human herpesvirus type-8 (HHV-8) infection in all cases and EBV infection in 70% of cases. Epstein-Barr virus (EBV) infection in PEL displays a latency I phenotype.', 'To clarify the pathogenesis and histogenesis of PEL by investigating (1) the lymphoma karyotype; (2) the expression status of the Met tyrosine kinase receptor and of its ligand hepatocyte growth factor (HGF); (3) the molecular profile of EBV, with particular focus on mutations of EBNA-1 genes, which are thought to affect viral tumorigenicity in EBV-infected neoplasms displaying the latency I phenotype.', 'Twenty-four PEL (nine cell lines and 15 primary specimens) formed the basis of the study. Karyotypes were investigated by conventional cytogenetics and fluorescent in situ hybridization (FISH) in selected cases. The expression status of Met and HGF was defined by multiple techniques, including RT-PCR, FACS analysis, immunocytochemistry, Western blot studies and ELISA. The molecular profile of EBNA-1 genes of EBV were investigated by DNA direct sequencing.', 'Trisomy 7, trisomy 12 and breaks at 1q21-q25 are recurrently associated with PEL. PEL consistently co-express Met and HGF both at the mRNA and protein level. Among aggressive B-cell lymphomas, Met/HGF co-expression appears to be relatively specific for PEL. The EBNA-1 gene of EBV displays a high degree of genetic heterogeneity in PEL, with no preferential association with one specific variant.'] Does molecular characterization of HHV-8 positive primary effusion lymphoma reveal pathogenetic and histogenetic features of the disease?