Role of Immunohistochemistry in Differentiating Hodgkin Lymphoma from Non-Hodgkin Lymphoma in Lymph Node Biopsies

Abstract

Introduction: Morphology alone can be insufficient to distinguish classical Hodgkin lymphoma (cHL) and nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL) from non-Hodgkin lymphomas (NHL) that share overlapping features (e.g., primary mediastinal large B-cell lymphoma [PMBL], T-cell/histiocyte-rich large B-cell lymphoma [THRLBCL], ALK-positive anaplastic large cell lymphoma [ALCL]). Immunohistochemistry (IHC) provides decisive lineage and checkpoint markers (CD30, CD15, PAX5, CD20, CD45, ALK, OCT2/BOB1, SOX11, cyclin D1, BCL6, MUM1/IRF4, PD-L1) and EBV-encoded RNA in situ hybridization (EBER-ISH) that help resolve diagnostic uncertainty.

Materials and Methods: We conducted a prospective observational study on consecutive lymph node biopsies over 24 months at a tertiary center. A tiered IHC panel was applied to all cases with equivocal morphology. Primary outcome was diagnostic accuracy for HL vs NHL; secondary outcomes included incremental yield over morphology, misclassification reduction, and effect on turnaround time (TAT) and costs.

Results: Among 180 evaluable cases, final diagnoses were cHL 52 (28.9%), NLPHL 12 (6.7%), DLBCL 60 (33.3%), FL 28 (15.6%), mantle cell lymphoma (MCL) 10 (5.6%), PTCL 10 (5.6%), and ALCL 8 (4.4%). A minimal panel (CD30, CD15, PAX5, CD20, CD45, EBER-ISH) achieved 96.2% sensitivity and 95.0% specificity for HL vs NHL. Adding OCT2/BOB1 and PD-L1 improved accuracy for cHL vs mimics (PMBL/THRLBCL) and identified PD-L1-high cHL. SOX11/cyclin D1 resolved MCL vs cHL look-alikes. Optimizing reflex panels reduced median TAT by 1.5 days and per-case IHC costs by 18%.

Conclusion: A tiered IHC algorithm centered on CD30/CD15/PAX5 with EBER-ISH, and reflex markers tailored to the differential (OCT2/BOB1, PD-L1, ALK, SOX11/cyclin D1), provides high accuracy and operational efficiency in separating HL from NHL.