Introduction And Pathology

Nodular lymphocyte-predominant Hodgkin's Lymphoma (NLPHL) is a unique subtype of Hodgkin's lymphoma (HL), which accounts for approximately 5% of cases and has a morphology, immunophenotype, clinical presentation, natural history, and prognosis that are distinct from classical HL (CHL). This variant of HL was first described in the 1930s and recognized not only for its unique morphology but also its more indolent clinical behavior. Jackson and Parker coined the term "paragranuloma"—a term that is sometimes still seen in the literature.1 Lukes and Butler used the term lymphocytic and histiocytic (L&H) and further divided this type into nodular and diffuse subtypes.2 At the 1966 Rye conference, four types of HL were recognized: nodular sclerosis, mixed cellularity, lymphocyte depletion, and lymphocyte predominance (LP).3 Although the Rye classification combined the nodular and diffuse subtypes of LPHL, subsequent studies continued to analyze the pathological and clinical differences between these two variants.4-6 With advances in pathology and, in particular, immunohistochemistry, hematopathologists appreciated that a purely morphologic classification system was inadequate. In fact, the morphologic classifications of LPHL actually included at least two biologically distinct types of HL. This distinction was recognized in the 1994 Revised European-American Lymphoma (REAL) classification, which separated "lymphocyte predominance (paragranuloma)" from the other types of HL and added a provisional subtype of CHL, "lymphocyte-rich classical" (LRCHL).7 More recently, the World Health Organization (WHO) classification separated HL into two broad, pathologically and clinically distinct categories: NLPHL and CHL.8 9 The pathologic characteristics are detailed in Chapter 71. Briefly, NLPHL is a monoclonal B-cell neoplasm characterized by a nodular, or a nodular and diffuse, polymorphous proliferation of scattered large neoplastic cells known as "popcorn" or "L&H" cells.9 Unlike the Reed-Sternberg cells of CHL, the L&H cell of NLPHL express the B-cell marker, CD20, but not CD15 or CD30. When the REAL/WHO criteria were applied to LPHL cases previously diagnosed by expert hematopathologists based on morphology alone, only three-quarters of the cases were still classified as LPHL.1011 Most of the other cases were reclassified as CHL and, in particular, LRCHL.

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