Kristie A Blum and Pierluigi Porcu

On the basis of differing morphologic, biologic, and clinical features described over the last 20 years, the currently accepted World Health Organization (WHO) Classification of Lymphoid Neoplasms recognizes two distinct clinical subtypes of Hodgkin's lymphoma (HL): classical HL and nodular lymphocyte-predominant HL.1 Classical HL is a monoclonal lymphoid neoplasm composed of malignant Reed-Sternberg cells, which are multinucleated B cells that are CD30 and CD15 positive, surrounded by a mixed inflammatory infiltrate consisting of nonneoplastic lymphocytes, eosinophils, histiocytes, plasma cells, and fibroblasts. Four histologic subtypes of classical HL that differ in the morphology of Reed-Sternberg cells and composition of the reactive infiltrate have been identified: nodular sclerosis HL (NS HL), lymphocyte-rich HL (LR HL), mixed cellularity HL (MC HL), and lymphocyte-depleted HL (LD HL). While there is considerable overlap among these subtypes, unique clinical features have been noted with each.

Recognized as a separate entity in the WHO classifi-cation,1 nodular lymphocyte-predominant HL is a monoclonal B-cell neoplasm characterized by a diffuse proliferation of large neoplastic cells [popcorn or lymphocytic and histiocytic (L&H) cells] that are CD20, CD79a, and CD45 positive and CD15 and CD30 negative, differing from Reed-Sternberg cells in classical HL.2 These cells are frequently surrounded by a background infiltrate of nonmalignant small lymphocytes. This subtype comprises 3-8% of all HL,3'4 and has distinct clinical features and patterns of relapse in several different trials and case series.5-9

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