Aggressive natural killer cell lymphoma presenting as an anterior mediastinal mass in a patient with acquired immunodeficiency syndrome

We report a case of aggressive natural killer cell lymphoma presenting as a n anterior mediastinal mass in an African-American man with acquired immuno deficiency syndrome. Histologically, the anterior mediastinal mass showed a diffuse dense infiltrate of atypical intermediate-sized and large lymphoid cells, as well as scattered immunoblasts with angiocentric and angiodestru ctive growth and extensive zonal necrosis. Similar lymphoid infiltrates wer e present in the patient's lungs, spleen, and bone marrow, accompanied by e xtensive lymphophagocytosis. Electron microscopic and cytologic examination s showed the presence of dense cytoplasmic granules. Immunophenotyping by f low cytometry and by immunohistochemistry yielded surface markers consisten t with a natural killer cell lymphoma. The Epstein-Barr virus genome and mo noclonality were detected by in situ hybridization and Southern blot analys is. Polymerase chain reaction confirmed the presence of type A Epstein-Barr virus. T-cell receptor gene rearrangement could not be identified by South ern blot analysis or polymerase chain reaction. To the best of our knowledg e, this is the first reported case of designated natural killer cell lympho ma from the mediastinum, as well as the first reported case of natural kill er cell lymphoma in a patient with acquired immunodeficiency syndrome. This tumor disseminated early and pursued a highly aggressive course. Epstein-B arr virus may play a role in the pathogenesis of this disease.