Large B-Cell Lymphoma With IRF4 Rearrangement Involving Lung

Abstract

Abstract Introduction/Objective Large B-cell lymphoma (LBCL) with IRF4 rearrangement is a new entity described in the 2017 WHO Classification of Tumors of Hematopoietic and Lymphoid Tissues. It is characterized by 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 adults with a 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 a case of LBCL in a 74-year-old female patient that presented with a lung nodule. Methods H&E staining, Immunohistochemistry and Fluorescence in-situ hybridization (FISH) were used to characterize this lesion. Results H&E stained sections of lung nodule biopsy showed diffuse proliferation of medium- to large-sized tumor cells. Immunohistochemistry showed tumor cells are positive for CD10, BCL6 and IRF4/MUM1. FISH showed rearrangement of IRF4, but is negative for MYC, BCL2 and BCL6 translocations. Conclusion To the best of our knowledge, this is the first case of LBCL with IRF4 rearrangement reported involving the lung in an old patient. Cases that show coexpression of CD10, BCL6 and IRF4/MUM1 should be tested for IRF4 rearrangement despite patient’s age and the site of disease. Generally, prognosis of this disease is favorable following chemotherapy with or without radiation. However, data are lacking regarding older patients and diseases involving atypical sites due to very limited number of cases reported earlier.