Classic KSHV/HHV-8-positive Primary Effusion Lymphoma (PEL): A Systematic Review and Meta-Analysis of Case Reports

Primary effusion lymphoma (PEL) is a large B-cell lymphoma growing within body-cavities caused by the Kaposi sarcoma-associated herpesvirus (KSHV)/human herpesvirus-8 (KSHV/HHV-8). It is mainly reported in HIV-infected patients. The uncommon occurrence in the elderly supports a form paralleling classic Kaposi sarcoma (KS), i.e. classic PEL, whose characteristics are relatively underexplored. To better understand the diagnostic modalities and clinical-epidemiological features of classic PEL, articles reporting cases of PEL were identified through MEDLINE/EMBASE databases (January 1998-July 2020) and screened according to PRISMA guidelines to extract individual-level data. A comparison was also performed between classic PEL and classic KS to evaluate similarities and differences. We identified 105 subjects (median age 77 years; 86% males), mainly from Mediterranean countries (52%, first Italy) and Eastern Europe (7%). Common comorbidities were heart failure (32%), cirrhosis (16%), and malignancy (20%) including lymphoid neoplasms. Pleural cavity was the commonest site (67%). PEL diagnosis was based on cytomorphology (89%), evidence of KSHV/HHV-8 infection (94%), EBV co-infection (28%) and clonality of IGH (59%), IGK (14%), TRG (9%) alone or in multiple combinations. Compared to KS, age (P<.001), gender-ratio (P=.08) and mortality (P<.001) were significantly higher in PEL, whereas the frequency of PEL as a second primary was similar (P=.44). This is the first systematic review of classic PEL case reports highlighting heterogeneity and lack of a uniform multidisciplinary approach at diagnosis, in the absence of specific guidelines as it happens for rare cancers. It is conceivable that classic PEL is still underdiagnosed in Mediterranean countries wherein KSHV/HHV-8 is endemic.