385 Abbreviations: FL, follicular lymphoma; DLBCL/HGBL, diffuse large B-cell lymphoma/high-grade B-cell lymphoma; AUC, area under the curve; FC, flow cytometry; LN, lymph node; PE, phycoerythrin; MFIr, median fluorescence intensity ratio; FS, forward scatter; SS, side light scatter; FSr, FS ratio; SSr, SS ratio; ROC, receiver operating characteristic; CI, confidence interval; IQR, interquartile range; Sens, sensitivity; Spec, specificity; PPV, positive predictive value; NPV, negative predictive value. 1 Department of Laboratory Hematology, ICO-Hospital Germans Trias i Pujol, Institut de Recerca Josep Carreras, Universitat Autònoma de Barcelona, Badalona, Spain 2 Department of Pathology, Hospital Germans Trias i Pujol, Universitat Autònoma de Barcelona, Badalona, Spain 3 Clinical Laboratory ICS-Metropolitana Nord, Core-Hematology Department, Hospital Germans Trias i Pujol, Badalona, Spain *To whom correspondence should be addressed. msorigue@iconcologia.net © American Society for Clinical Pathology 2019. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com Flow Cytometry in the Differential Diagnosis of CD10-Positive Nodal Lymphomas Marc Sorigue, MD, 1 * Mireia Santos-Gomez, MD, 1 Martina Comes, MD, 1 Minerva Raya, 1 Sara Vergara, 1 Gustavo Tapia, MD, PhD, 2 José-Tomas Navarro, MD, PhD, 1 Cristian Morales-Indiano, MD, 3 Jordi Junca, MD, PhD 1 Laboratory Medicine 2020;51:385-393 DOI: 10.1093/labmed/lmz085 ABSTRACT Background: Differences between follicular lymphoma (FL) and diffuse large B-cell lymphoma/high-grade B-cell lymphoma (DLBCL/HGBL) by fow cytometry are underexplored. Methods: We retrospectively assessed fow cytometry results from 191 consecutive lymph node biopsies diagnosed with FL or DLBCL/HGBL. Results: The only parameters that differed between the 2 groups in the derivation cohort were forward scatter and side scatter (P < 10 –6 ; area under the curve [AUC], 0.75–0.8) and %CD23 (P = .004; area under the receiver characteristic operating curve, 0.64). However, since light scatter characteristics did not distinguish between grade 3 FL and DLBCL/HGBL, we set out to develop a model with high sensitivity for the exclusion of the latter. Several models, including FS and %CD23, were tested, and 2 models showed a sensitivity of >0.90, with negative predictive values of ≥0.95, albeit with low specifcity (0.45 to 0.57). Conclusion: Two simple models enable the exclusion of DLBCL/HGBL with a high degree of confdence. Keywords: CD10, fow cytometry, follicular lymphoma, diffuse large B-cell lymphoma, high-grade B-cell lymphoma, light scatter Flow cytometry (FC) is a rapid and reproducible tool to char- acterize lymphoid populations reliably. Although the diagnosis of lymphoma should be based on the histological analysis of the specimen, FC has a relevant role in guiding the diagnostic process, making it quicker and cheaper and offering clinicians and patients an early clue into the fnal diagnosis. CD10 is, alongside CD5, the antigen that guides the diagnostic process of B cell disorders. 1 In lymph nodes (LN), it most often (although not exclusively) suggests the presence of a germinal-center derived malignancy. However, there are only a few series examining the cytometric differences between the most common entities within this group, follicular lymphoma (FL) and diffuse large B-cell lymphoma/high-grade B-cell lymphoma (DLBCL/HGBL). 2,3 Importantly, a key diagnostic difference, the presence of LN follicles/follicular dendritic cells, is not straightforwardly assessed by FC. This suggests that FC may have a limited role to play in this differential diagnosis. The purpose of this study was to interrogate a cohort of patients with a diagnosis of germinal center-derived malig- nancies for cytometric differences between FL and DLBCL/ HGBL. Materials and Methods Study Population We screened all LN studies tested in our FC unit between January 2011 and April 2019 and with a World Health Downloaded from https://academic.oup.com/labmed/article/51/4/385/5677282 by guest on 08 February 2023