Case Series: Large B-cell Lymphoma with IRF4 Rearrangement Involving the Lung and the Tonsil in Two Different Patients

Abstract

Introduction/Objective Large B-cell lymphoma (LBCL) with IRF4 rearrangement is a new entity described in the 2017 WHO classification. It is characterized by a monotonous proliferation of medium to large sized cells with strong expression of IRF4/MUM1 and IRF4 rearrangement. It accounts for only 0.05% of all diffuse LBCLs and affects predominantly children and young adult with median age of 12 years. The reported sites of disease include lymph nodes of head and neck, Waldeyer ring and gastrointestinal tract. Here, we report two cases of Large B-cell Lymphoma with IRF4 rearrangement in two female patients, 73-year old and 71-year old respectively. The first patient presented with a lung nodule, while the second presented with right palatine tonsillitis. Hematoxylin and Eosin staining, immunohistochemistry and Fluorescence In-Situ Hybridization were used to characterize the lesions. H&E stained sections of the lung nodule biopsy from the first patient showed diffuse proliferation of medium- to large-sized cells (Figures A and B). Immunohistochemistry shows tumor cells are positive for CD20 (figure C), CD10, BCL6, and IRF4/MUM1(figure D). FISH study shows that tumor cells carry the IRF4 rearrangement but are negative for MYC, BCL2, and BCL6 translocations. To the best of our knowledge, this is the first case of LBCL with IRF4 rearrangement reported involving the lung in an older patient. H&E stained sections of the right palatine tonsil from the second patient shows effacement of the normal architecture which is replaced by sheets of large lymphoid cells. Immunohistochemistry shows tumor cells positive for CD20, CD10, BCL-6, BCL-2, MUM-1, C-MYC, and Ki-67 (80%). FISH study shows that tumor cells carry the IRF4 rearrangement which is consistent with a diagnosis of LBCL with IRF4 rearrangement. Methods/Case Report NA. Results (if a Case Study enter NA) NA. Conclusion NA.