Comparative genomic hybridization of eight PEL cases showed gain of chromosomes 12 and X in three and two cases, respectively, and amplification within the 1q region in two cases.81BCL-2, BCL-6 and MYC genes were not rearranged, and mutations in MYC, HRAS, KRAS, NRAS and TP53 genes were not found.74 Clonal rearrangement of the Ig gene is seen in most cases and can be used for determining lineage. This evidence concerns the gene NRAS and primary effusion lymphoma.