Clinical boundaries in adult cases of large B cell lymphoma with IRF4 rearrangement

AimsLarge B-cell lymphoma with IRF4 rearrangement (LBCL-IRF4) is a recently described entity included in the revised 4th edition of the WHO Classification of Haematolymphoid Tumours (2017). Here we highlight the difficulties in classification of those cases which arise in adult patients with unusual clinical features.ResultsWe present three cases with morphological and immunohistochemical features consistent with large B-cell lymphoma arising in adult patients, which were found to have isolated IRF4 rearrangements on FISH analysis. Each patient presented with advanced-stage disease and had a history of immunosuppression; clinical features that are not typical of LBCL-IRF4 and which make the distinction from DLBCL, not otherwise specified (NOS) challenging.ConclusionWe propose that the clinical boundaries of LBCL-IRF4 arising in adult patients need further delineation to allow distinction from true cases of DLBCL, NOS.