BACKGROUND: Plasmablastic lymphoma (PBL) is a rare form of non-Hodgkin lymphoma that was once believed to occur primarily in the oral cavity of human immunodeficiency virus-positive individuals. Numerous extraoral sites have also been reported to date. To the authors' knowledge, however, only 3 reports in the literature describe its cytologic features. In the current study, the cytologic findings in 5 additional patients are reported, 3 of whom had concomitant second malignancies. The goal of the current study was to define the cytomorphologic features that may help to distinguish PBL from other mimics. METHODS: Five cases were identified from the pathology files for which cytology was available. The presence of the following was evaluated: cellularity, plasmablastic cells, background necrosis (BN), single-cell necrosis (SCN), lymphoglandular bodies (LGB), tingible-body macrophages (TBM), 3-dimensional clusters/sheets, and cytoplasmic vacuoles. RESULTS: The patients included 3 women and 2 men with an age range of 40 to 57 years. Two patients had the acquired immunodeficiency syndrome and 3 had second non-PBL related malignancies including endometrial carcinoma, lung adenocarcinoma, and small lymphocytic lymphoma. The most common cytologic features were hypercellularity (80%), plasmablastic cells (73%), SCN (73%), BN (87%), and LGB (66%). TBMs (33%) and clusters/sheets (47%) were the least common features. CONCLUSIONS: Although no 1 cytologic feature is diagnostic of PBL, a constellation of findings should raise suspicion. These include hypercellular specimens with abundant plasmablastic cells, LGB, SCN, and BN. However, although these findings may suggest PBL, a definitive diagnosis requires adjunctive studies including immunohistochemistry and flow cytometry. As with any lymphocyte-rich aspirate, additional material should be collected for these studies. Over-reliance on adjuvant studies is discouraged because the PBL immunophenotype is not considered standard. (c) 2008 American Cancer Society.