Cytologic and immunocytochemical features of EBV negative primary effusion lymphoma: Report on seven Japanese cases

Primary effusion lymphoma (PEL) is very rare type of non-Hodgkin's lymphoma (NHL) usually confined to the body cavities such as the pleural space, pericardium, and peritoneum. PEL is a human herpes virus-8 (HHV-8)-associated lymphoma and commonly observed in human immunodeficiency virus (HIV)-infected patients. However, HIV-infected patients are extremely fewer in Japan in comparison with those in Western countries; PEL is usually not associated with HIV infection in Japan. This report presents seven Japanese cases of PEL. In situ hybridization revealed that the PEL cells were negative for EBV in all cases. An immunocytological analysis showed that only one case was positive for HHV-8, and PEL cells were positive for CD20 in all cases. MUM1 was positive, but CD10 and CD138 were negative in six cases. One case each was positive for CD30 and BCL-6. The phenotypic patterns of HIV-related is BCL6−/MUM1+/CD138+, thus, the phenotypic findings observed by immunocytochemistry in this study were somehow different from those reported in Western countries. However, the cytomorphological features of PEL cells showed large cell size, abundant basophilic cytoplasm, coarse chromatin, and occasional binucleated or multinucleated cells, similar to a large cell immunoblastic and anaplastic large cell lymphoma, indicating that the cytomorphological characteristics of PE cells in Giemsa and Papanicolaou stain were consistent with those reported abroad. The prognosis for PEL in these cases was poor, but the survival time was variable ranging from 1 month to 54 months, and was different from that of Western cases. No p16/CDKN2A expression was observed, and one case showed PEL cells with a BLIMP1 mutation. Diagn. Cytopathol. 2009. © 2009 Wiley-Liss, Inc.