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

Large B-cell lymphoma (LBCL) with interferon regulatory factor 4 (IRF4) rearrangement is characterized by the monotonous proliferation of medium- to large-sized cells with strong expression of IRF4/multiple myeloma oncogene 1 (MUM1). It predominantly affects children and young adults with a median age of 12. The reported disease sites include head and neck lymph nodes, the Waldeyer's ring, and the gastrointestinal tract. Here, we report two cases of LBCL with IRF4 rearrangement in 73-year-old and 71-year-old patients. The first patient presented with a lung nodule, while the second patient presented with right palatine tonsillitis. To our knowledge, LBCL with IRF4 rearrangement involving the lung in an elderly patient has not been previously reported.