Expansion of PD1-positive T Cells in Nodal Marginal Zone Lymphoma: A Potential Diagnostic Pitfall

• Published in: The American journal of surgical pathology Vol. 44; no. 5; p. 657
• Main Authors: Egan, Caoimhe, Laurent, Camille, Alejo, Julie C, Pileri, Stefano, Campo, Elias, Swerdlow, Steven H, Piris, Miguel, Chan, Wing C, Warnke, Roger, Gascoyne, Randy D, Xi, Liqiang, Raffeld, Mark, Pittaluga, Stefania, Jaffe, Elaine S
• Format: Journal Article
• Language: English
• Published: United States 01.05.2020
• Subjects: Adult; Aged; Aged, 80 and over; Biomarkers, Tumor - analysis; Cell Proliferation; Diagnosis, Differential; Diagnostic Errors; Europe; Female; Humans; Lymphoma, B-Cell, Marginal Zone - immunology; Lymphoma, B-Cell, Marginal Zone - pathology; Lymphoma, T-Cell, Peripheral - immunology; Lymphoma, T-Cell, Peripheral - pathology; Male; Middle Aged; North America; Predictive Value of Tests; Programmed Cell Death 1 Receptor - analysis; T-Lymphocytes, Helper-Inducer - immunology; T-Lymphocytes, Helper-Inducer - pathology; Tumor Microenvironment; North America; Europe
• ISSN: 1532-0979
• DOI: 10.1097/PAS.0000000000001414

The diagnosis of nodal marginal zone lymphoma (NMZL) can be challenging, with the differential diagnosis including other low-grade B-cell lymphomas, reactive hyperplasia, and even some cases of peripheral T-cell lymphoma (PTCL). PTCL may have a perifollicular growth pattern mimicking NMZL. We and others have noted an atypical distribution of T-follicular helper (TFH) cells in some cases of NMZL. This study was prompted by the diagnosis of NMZL in several cases in which a marked increase of TFH cells, as determined by staining for programmed death-1 (PD1), had prompted suspicion for a diagnosis of PTCL. We analyzed PD1 staining in 48 cases of NMZL to characterize the extent and pattern of the PD1-positive infiltrate. Three main patterns of PD1 staining were identified: follicular pattern (peripheral, n=16; central, n=9; mixed, n=3), diffuse pattern (n=4), and a reduced or normal staining pattern in residual follicles (n=16). A comprehensive analysis of other TFH markers was undertaken in 14 cases with a high content of PD1-positive cells that were confirmed as B-cell lymphoma by clonality analysis. We describe in detail 5 of these cases in which PTCL was an initial consideration. This study illuminates the diverse immunohistochemical patterns encountered in NMZL and highlights a diagnostic pitfall important for diagnostic accuracy.