CD7 and CD56-positive primary effusion lymphoma in a human immunodeficiency virus-negative host

Primary effusion lymphoma is an entity with distinctive features. The majority of cases are diagnosed in patients infected with human immunodeficiency virus. We report a case of pleural-based primary effusion lymphoma in an elderly patient negative for human immunodeficiency virus. By flow cytometry, lymphoma cells expressed CD7, CD38, CD45, CD56, HLA-DR, and kappa surface light chains. A monoclonal rearrangement of the immunoglobulin heavy chain and the presence of human herpesvirus 8 genome were detected. Our case lacked CD30 or CD138 with expression of surface light chains. There was strong expression of CD7 and CD56. These findings are unusual or unique in primary effusion lymphoma. Our report suggests that aberrant expression of T cell and natural killer cell markers can be seen in primary effusion lymphoma.