Classification of aggressive B-cell lymphomas : News and open questions

Abstract

The 5th edition of the WHO classification (WHO-HAEM5) and the International Consensus Classification (ICC) show abroad consensus in the categorization of aggressive, large B‑cell lymphomas with expected minor impact only on the daily diagnostic routine. The changes compared to the 2017 revised WHO-HAEM4R are moderate and include updated names of entities, sharpened diagnostic criteria, and upgrades from provisional to definite entities. The definition of the most common aggressive B‑cell lymphoma, diffuse large B‑cell lymphoma (DLBCL), not otherwise specified (NOS), remains unchanged, and both classifications strongly encourage subtyping into germinal center B‑like (GCB) or the activated B‑like (ABC or non-GCB) DLBCL. DLBCL, NOS, should be separated from other large B‑cell lymphomas including large B‑cell lymphoma with IRF4 rearrangement (upgraded to adefinite entity in both classifications) and large-cell/high-grade B‑cell lymphomas with 11q aberration. Aggressive B‑cell lymphomas with MYC and BCL2 rearrangements form amolecularly distinct group and are listed as definite entities in both classifications. This is in contrast to the more heterogeneous group of aggressive B‑cell lymphomas with MYC and BCL6 rearrangements that are recognized as aprovisional entity in the ICC, while they fall into the DLBCL, NOS, or the HGBL, NOS, groups in the WHO-HAEM5.