Small B-cell lymphomas. Diagnosis of malignant lymphomas in 2014

Abstract

The 2008 WHO classification of tumors of hematopoietic and lymphoid tissues has adopted consensus guidelines for the definition of well-defined entities. The major principle of the classification is the recognition of distinct diseases according to a combination of morphology, immunophenotype, genetic, molecular and clinical features. These disease entities are stratified according to their cell lineage and their derivation from precursor or mature lymphoid cells. Although the new 2008 WHO classification intentionally does not divide lymphomas by grade, traditionally mature B-cell lymphomas composed mainly of small lymphocytes have been called low-grade lymphomas. These small B-cell lymphomas include chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL), follicular lymphoma (FL), nodal marginal zone lymphoma (MZL), MALT lymphoma, hairy cell leukemia, and lymphoplas-macytic lymphoma (LPL). An entity that should be included in the differential diagnosis of lymphomas composed mainly by small lymphocytes but with a rather aggressive behaviour is mantle cell lymphoma (MCL). As a consequence of new and better available techniques in routine diagnosis, an increased recognition of early and precursor lesions of lymphoid neoplasms has emerged. This talk aims to review the morphological and phenotypic characteristics of the most frequent small B-cell lymphomas and expand on emerging concepts like, BCL2 negative FL, grading of EL, Pediatric FL, and indolent and cyclin Dl negative MCL, differential diagnosis of CD5+ low-grade lymphomas and more.