Selective loss of B-cell phenotype in lymphocyte predominant Hodgkin lymphoma.

The neoplastic Reed-Sternberg cells characteristic of classical Hodgkin's lymphoma (cHL) are of B-cell origin but they almost always show striking loss of a range of B-cell-associated molecules. In contrast, the neoplastic cells found in lymphocyte predominant Hodgkin's lymphoma (LPHL) (L&H cells) are traditionally thought of as possessing the full repertoire of features associated with germinal centre B cells (eg BCL-6 expression, 'ongoing' Ig gene mutation). In the present paper, we report an extensive phenotypic analysis of L&H cells which revealed down-regulation of a number of markers associated with the B-cell lineage (eg CD19, CD37) and with the germinal centre maturation stage (eg PAG, LCK). The promoter methylation status of three of these down-regulated genes (CD10, CD19, and LCK) was further studied in microdissected L&H cells, and this revealed that their promoters were unmethylated. In contrast, these genes showed promoter methylation in cell lines derived from CHL. Further investigation of the mechanisms responsible for the deregulation of these molecules in L&H cells may provide new insights into the genetic abnormalities underlying LPHL.

Anaplastic large cell lymphoma: a concept reviewed.

The development of the concept of anaplastic large cell lymphoma is reviewed. The subtypes of the tumor proposed in the literature, including the so-called Hodgkin's-like variant, are discussed both on morphological and clinical grounds. The more recent information on the genetic and molecular characteristics of the tumor (i.e. 2;5 translocation, formation of the NPM/ALK hybrid gene, and production of a specific protein) are presented: their possible implications in the future classification and clinical management of the neoplasm are discussed.