Cytokeratin-positive primary effusion lymphoma: a diagnostic challenge.

The article describes the case of an 88-year-old human immunodeficiency virus-negative man. The patient had a history of chronic obstructive pulmonary disease and pulmonary tuberculosis and he presented with dyspnea. He was diagnosed with primary effusion lymphoma but with an unusual cytokeratin expression, adding to the growing list of lymphomas that can show cytokeratin positivity.