The spectrum of the cytopathological features of Primary Effusion Lymphoma (PEL) and HHV8-related lymphoproliferative disorders.

OBJECTIVE: HHV 8-related lymphoproliferative disorders are a complex and heterogeneous group of entities and some of them are still eminently diagnosed by cytopathology. In a routine lab, these lesions accounted for less than 1% of the effusion fluids samples. However, they may represent around 30% of all the lymphoma diagnosis from effusion cytological samples and their consideration in the diagnostic flow chart is mandatory, especially in HIV-positive patients. METHODS: The paper analyzes a retrospective series of cytological specimens from cavities effusions (N = 605). Five HHV8-related lymphoproliferative processes were recruited. A combination of morphological criteria (enhanced with MGG staining), cell block-based immunocytochemistry and flow cytometry is required for the final characterization. RESULTS: The identification of malignant cells may be insidious. Some specimens are particularly rich, easily leading to suspect a lymphoproliferative process, whereas in the other cases the presence of abundant reactive mesothelial cells, histiocytes, neutrophils, small reactive T and B lymphocytes may obscure the neoplastic process. The biological behaviour may be very heterogeneous and a standardized therapy for these cases is still lacking, although some patients may benefit from the antiretroviral therapy in HIV-setting. CONCLUSIONS: The present case series highlights some emblematic findings of these entities to reaffirm useful cytopathological diagnostic criteria, stressing the crucial role of the appropriate technical processing of effusion fluids to obtain the best performances.