A distinct non-Hodgkin s lymphoma (NHL) entity that grow in the body cavities as lymphomatous effusions in the absence of clinically identifiable tumor masses has been defined as primary effusional lymphoma (PEL). This lymphoma characterized by distinetive morphology, immunophenotype, genotype and association with Kaposi s sarcoma-associated herpesvirus (KHSV)/human herpesvirus-8 (HHV-8) infection. In this minireview, the clinico-pathological and biological characteristics of PELs are summarized.