Review ArticlesA Simple and Practical Guide for Triaging Lymphocyte-rich Effusions for Ancillary StudiesLiu, Chih-Yi MD*; Chuang, Shih-Sung MD†Author Information *Division of Pathology, Sijhih Cathay General Hospital, New Taipei City †Department of Pathology, Chi-Mei Medical Center, Tainan, Taiwan The authors have no funding or conflicts of interest to disclose. Reprints: Shih-Sung Chuang, MD, Department of Pathology, Chi-Mei Medical Center, 901 Chung-Hwa Road, Yong-Kang District, Tainan 71004, Taiwan (e-mail: [email protected]). All figures can be viewed online in color at www.anatomicpathology.com. Advances In Anatomic Pathology: March 2021 - Volume 28 - Issue 2 - p 94-104 doi: 10.1097/PAP.0000000000000290 Buy Metrics Abstract Lymphocyte-rich effusions of the body cavities may represent a reactive/benign condition, primary effusion lymphoma, or systemic lymphoma with secondary malignant effusion, either as initial presentation or as a late complication. Cytomorphologic examination is essential and fundamental for diagnosis and may provide important clues to the nature of diseases. However, based on morphology alone, cytologic diagnosis of lymphocyte-rich effusions could be very challenging, particularly when the lymphocytes are small. Cytologists/cytopathologists might be uncertain when a lymphocyte-rich effusion specimen warrants a comprehensive hematopathologic workup. Herein we present a simple and practical algorithmic approach. On the basis of the cytomorphology of lymphocytes (small vs. large cells), presence or absence of cellular atypia, and clinical information (an earlier history or current lymphoma), the lymphocyte-rich effusion samples could be triaged for ancillary studies including immunophenotyping and molecular assays if indicated. Incorporation of cytomorphology, correlation with clinical information, and appropriate application of various ancillary techniques is mandatory for a correct diagnosis of lymphocyte-rich effusion specimens. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.