Aggressive B‐cell lymphomas with a primary bone marrow presentation

Abstract

Aggressive B‐cell lymphomas comprise a heterogeneous spectrum of disease. A primary diagnosis in the bone marrow (BM) may be challenging in terms of diagnostic classification and clinical handling due to limited architectural information. Aggressive B‐cell lymphomas can be subdivided into entities presenting typically primarily in the BM, and cases with BM involvement where the bulk of disease is present in other organs. One main topic at the 2018 BM workshop of the European Association of Haematopathology/Society of Hematopathology therefore was aggressive B‐cell lymphomas with primary BM presentation. The spectrum of cases submitted to this topic gave a good overview of commonly encountered problems, as well as unusual manifestations and highlighted areas of imprecise disease definitions and diagnostic grey zones. The categories submitted to the workshop included cases of Burkitt lymphoma with unusual features, high‐grade B‐cell lymphomas (HG‐BCL) with and without so‐called double/triple hit and diffuse large B‐cell lymphoma (DLBCL) with primary BM presentation. Areas of difficulties included the morphological boundaries of HG‐BCL, not otherwise specified, cases with MYC and BCL2 or BCL6 translocations and TdT expression, which were categorized as B‐lymphoblastic lymphoma/leukemia if most cells showed TdT positivity, and the clinico‐pathologic overlap between intravascular large B‐cell lymphoma, DLBCL CD5+ and DLBCL with primary presentation in BM, spleen and liver. This review summarizes our understanding of the main aggressive B‐cell lymphoma categories with common primary BM presentation and potential problem areas, and makes suggestions for the immunophenotypic and genetic work‐up, illustrated by the interesting and challenging cases submitted to the workshop.