The utility of multiparametric flow cytometry in the detection of primary effusion lymphoma (PEL).

Primary effusion lymphoma (PEL) is a rare B cell lymphoproliferative disorder that arises predominantly in body cavities causing malignant effusions. The incidence of PEL is very low, accounting for approximately 4% of all HIV-associated non-Hodgkin lymphomas. PEL has also been described in elderly patients and after solid-organ transplantation. It is associated in all cases with human herpes virus 8 (HHV8). We describe a case of PEL in a 88-year-old HIV-negative woman who presented with progressive dyspnea and moderate right-sided pleural effusion without significant lymphadenopathies or other effusions. The cytological study of the pleural fluid revealed a dense proliferation of large plasmablastic cells. A six-color multiparametric flow cytometry immunophenotyping study was carried out, and revealed 45% of large in size and high cellular complexity cells positive for CD45 (dim), CD38, CD138, CD30 and HLA-DR; and negative for CD19, CD20, cytoplasmatic CD79a, surface and cytoplasmic light chains Kappa and Lambda, CD3, CD4, CD5, CD7, CD8, CD28, CD56, CD81, and CD117. In situ hybridization for EBV-encoded smalI RNA was negative and immunohistochemistry for Kaposi sarcoma herpesvirus (HHV8) confirmed the diagnosis of PEL. Our results confirm that flow cytometry bring useful data in the diagnosis of large-cell lymphomas involving body cavities.