Cytogenetics in the management of mature B-cell non-Hodgkin lymphomas: Guidelines from the Groupe Francophone de Cytogénétique Hematologique (GFCH).

Non-Hodgkin lymphomas (NHL) consist of a wide range of clinically, phenotypically and genetically distinct neoplasms. The accurate diagnosis of mature B-cell non-Hodgkin lymphoma relies on a multidisciplinary approach that integrates morphological, phenotypical and genetic characteristics together with clinical features. Cytogenetic analyses remain an essential part of the diagnostic workup for mature B-cell lymphomas. Karyotyping is particularly useful to identify hallmark translocations, typical cytogenetic signatures as well as complex karyotypes, all bringing valuable diagnostic and/or prognostic information. Besides the well-known recurrent chromosomal abnormalities such as, for example, t(14;18)(q32;q21)/IGH::BCL2 in follicular lymphoma, recent evidences support a prognostic significance of complex karyotype in mantle cell lymphoma and Waldenström macroglobulinemia. Fluorescence In Situ Hybridization is also a key analysis playing a central role in disease identification, especially in genetically-defined entities, but also in predicting transformation risk or prognostication. This can be exemplified by the pivotal role of MYC, BCL2 and/or BCL6 rearrangements in the diagnostic of aggressive or large B-cell lymphomas. This work relies on the World Health Organization and the International Consensus Classification of hematolymphoid tumors together with the recent cytogenetic advances. Here, we review the various chromosomal abnormalities that delineate well-established mature B-cell non-Hodgkin lymphoma entities as well as newly recognized genetic subtypes and provide cytogenetic guidelines for the diagnostic management of mature B-cell lymphomas.