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Introduction: Human herpes virus 8‐related lymphoproliferative disorders are a complex and heterogeneous group of entities and some of them are eminently diagnosed by cytopathology. In a routine laboratory, these lesions account for less than 1% of the effusion fluids samples. However, they represent up to 30% of all the lymphoma diagnosis from effusion cytological samples and their consideration in the diagnostic flow chart is mandatory, especially in human immunodeficiency virus‐positive patients. Methods: A retrospective series of cytological specimens from cavity effusions (n = 605) were analysed. Five human herpes virus 8‐related lymphoproliferative processes were recruited. A combination of morphological criteria (enhanced with May‐Grünwald Giemsa staining), cell block‐based immunocytochemistry and flow cytometry were undertaken for final characterisation. Results: The identification of malignant cells may be difficult. Some specimens are particularly rich, easily leading to suspect a lymphoproliferative process, whereas in 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 standardised therapy for these cases is still lacking, although some patients may benefit from antiretroviral therapy in a human immunodeficiency virus setting. Conclusions: The present case series highlights some characteristic 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. The cytopathological features of PEL in HIV patients may be very heterogeneous. The current definition of the entity embraces cases with different clinical potential and pathological findings; future investigations on the pathogenesis of this rare entity will probably elucidate the exact characteristic of this group of B‐cells lymphomas. This group of disorders represents an exception in hematopathology since cytopathology is often mandatory and still plays a key role in their diagnosis. [ABSTRACT FROM AUTHOR]