Primary effusion lymphoma is a large cell non-Hodgkin lymphoma localized predominantly in body cavities and occasionally in extracavitary regions. It presents with characteristic lymphomatous effusions in the absence of solid tumor masses, and pleural, peritoneal, and pericardial spaces are most often involved. It is typically associated with human herpesvirus 8 infection in immunocompromised individuals, in the setting of human immunodeficiency virus infection, organ transplantation, or in rare cases advanced age. Histologically, primary effusion lymphoma is characterized by atypical lymphoid cells of B-cell lineage with large nuclei and prominent nucleoli. Demonstration of human herpesvirus 8 latent antigens is required for diagnosis, and treatment modalities are limited at this time. In this review, we aim to summarize clinicopathologic features of this rare and unique entity.