Application of Hans Algorithm for Subcategorization of Diffuse Large B-Cell Lymphoma in Fine-Needle Aspiration Biopsy Cytology

Abstract

Introduction: Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous disease with remarkably variable clinical presentation and outcome. Hans algorithm subclassified DLBCL into prognostically distinct molecular subtypes by using immunohistochemistry (IHC). Fine-needle aspiration biopsy cytology (FNABC) is a first-line diagnostic modality in lymphadenopathy. The study aims to perform IHC on FNABC cell blocks (CBs) for subclassifying according to the Hans algorithm and correlate with case-matched histopathology. Methods: This was a retrospective study carried out between January 2017 and December 2019. All DLBCL FNABC cases with CBs and smears and which had follow-up histopathology were included in the study. Detailed cytomorphological evaluation and CD10, B-cell lymphoma 6 (BCL6), and multiple myeloma oncogene 1 IHCs were performed on CBs. The cases are divided into 3 distinct molecular subtypes based on the Hans algorithm as germinal centre B-cell (GCB), activated B-cell (ABC), and unclassified subtypes. The results were compared with the final histopathology. Results: A total of 44 cases were diagnosed as DLBCL, and 33 cases with sufficient material for further IHC were included in the study. Twelve cases were of the GCB type, 19 were of the ABC type, and 2 remained unclassified. Follow-up histopathology was available in 20 cases. Overall, histopathological concordance was found in 95% of cases (19/20). The single discordant case was classified as GCB on FNABC and was ABC on histopathology. Conclusion: FNABC with CBs is an acceptable alternative to biopsy for providing a complete diagnosis of DLBCL as per the current WHO classification.