Hodgkin lymphoma: histological features and classification

Haema 2012; 3(3): 185-189

by Penelope Korkolopoulou, Georgia Levidou, Efstratios Patsouris

First Department of Pathology, Laiko Hospital, University of Athens, Medical School, Athens, Greece

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Abstract

Hodgkin lymphoma (HL) is classified into two major types, namely nodular lymphocytic predominance (NLPHL) and classical HL (CHL) which have distinct morphological, molecular and clinical features. NLPHL is characterized by a nodular growth pattern and the presence of monoclonal neoplastic “pop-corn” B cells (CD20, CD79a, PAX-5+) with a distinctive immunophenotype (BCL-6, CD45, OCT-2 and BOB-1+, CD15- CD30-), within a network of dendritic cells rich in mature B and T (CD4+, CD57+) lymphocytes. A variety of morphological subtypes have been described but without any clinical relevance. Recent data suggest that NLPHL cases with micrornodular pattern, in which small germinal centers (GCs) or broken up GCs are present, should be regarded as an early lesion limited to the GCs (“in situ” lymphoma). CHL is further classified into four subtypes; nodular sclerosis, mixed cellularity, lymphocyte-rich and lymphocyte-depleted classical HL. The hallmark of CHL is Hodgkin and Reed-Sternberg (RS) cells, which bear a characteristic immunophenotype (CD30+, CD15+ CD45- CD20-/+, PAX-5 faintly+) and are located within a polymorphous reactive cellular background. In par- ticular, nodular sclerosing CHL is characterized by bands of fibrocollagenous tissue surrounding nodules of inflammatory background cells containing Hodgkin and RS cells, often with a lacunar morphology. In mixed cellularity CHL, Hodgkin and RS cells are mostly EBV+ and are scattered in a polymorphous reactive background. According to the latest WHO classification, cases of CHL that cannot be otherwise classified are placed into the mixed cellularity category. Lymphocyte-rich CHL has a nodular growth pattern composed predominantly of small B lymphocytes containing atrophic, eccentrically placed GCs. The RS cells are located within the nodules or in their expanded mantle zone but not outside them. Finally, lymphocyte-depleted CHL is characterized by the presence of many Hodgkin/RS cells and decreased number of lymphocytes.