Summary
Diffuse large B-cell lymphoma (DLBCL) is an aggressive non-Hodgkin's lymphoma (NHL) that requires treatment at initial diagnosis. Treatment decisions may be guided by staging investigations, which include assessment of bone marrow (BM). Traditionally this assessment has included light microscopic examination of the bone marrow aspirate and trephine biopsy. Ancillary testing—including immunophenotyping using flow cytometry on BM aspirates, immunohistochemistry (IHC) on BM trephines and molecular studies using immunoglobulin heavy (IgH) or light (IgL) chain gene rearrangements—are performed as required to aid histological diagnosis. This review examines the evidence for the routine use of ancillary tests in the initial staging of DLBCL, including the limitations, potential pitfalls and possible clinical implications of their use in this setting.