ABSTRACT
Plasmablastic lymphoma (PBL) is a distinctly rare neoplasm believed to arise from post-germinal center, terminally differentiated, activated B cells before transformation to plasma cells; and predominantly affecting human immunodeficiency virus (HIV) infected or immunodeficient males. Here, we report a rare case of primary PBL of bone marrow in an immunocompetent male, the diagnosis of which is complicated by the overlapping morphology and immunophenotype with several large cell lymphomas and plasma cell neoplasms; and showing dramatic response to anti-CD30 monoclonal antibody based therapy. We discuss the immunohistochemistry based approach and the possible diagnostic pitfalls in such cases. The inclusion of markers of plasmablastic differentiation in the diagnostic panel of large cell lymphomas is essential to avoid misclassification of these rare lymphomas.