Evaluation of the frequency of benign reactive lymphocytosis and lymphoproliferative disorders by flow cytometry in patients with persistent lymphocytosis in peripheral blood

Introduction: Lymphocytosis is characterized by an elevation in the absolute lymphocyte count (ALC) to over 4000 lymphocytes per microliter among adults. In lymphocytosis, the important matter is whether lymphocytosis is a benign reactive condition or a neoplastic lymphoproliferative disorder (LPD), which can be determined by immunophenotyping methods by flow cytometry. Objectives: Due to the need to use flow cytometry to confirm the diagnosis of patients with lymphocytosis, the purpose of this study was to compare the frequency of benign reactive lymphocytosis and LPDs in patients with persistent lymphocytosis using flow cytometry in the peripheral blood and report the results based on the patient’s demographic characteristics. Materials and Methods: This study was a cross-sectional study and the study population was all peripheral blood samples referred to Seyed Al-Shohada hospital in Isfahan to study the cause of absolute and persistent lymphocytosis by immunophenotyping analysis through flow cytometry between 2015 and 2020. Inclusion criteria were patients over 18 years of age with absolute lymphocytosis in complete blood count (CBC) or peripheral blood smear (PBS) who were examined by flow cytometry. Results: This study involved 222 samples, 139 (62.6%) of the cases were male. The mean age was 60.41 (15.91) years. All samples had absolute lymphocytosis and were divided into two groups: benign, with 62 (27.9%), and malignant, with 160 (72.1%). Conclusion: The relationship between gender and malignancy showed that the male gender was associated with an increased risk of malignancy. The mean age between the two groups of malignant and benign was determined by independent t test, and it was shown that the mean (±standard deviation) age of malignant cases is higher than the mean age of benign cases. It is recommended that cases of suspected lymphoproliferative cases and cases with cell counts below the lymphocytosis threshold be investigated in separate studies.