Low-grade follicular lymphoma with interferon regulatory factor-4 rearrangement: Expanding the spectrum of interferon regulatory factor-4-rearranged lymphomas.

In recent years, the recognition of distinct lymphoma entities has expanded with advancements in molecular characterization. Large B-cell Lymphoma with interferon regulatory factor-4 (IRF4) rearrangement (LBCL-IRF4-R) is one such entity. We present a case of classic low-grade follicular lymphoma with IRF4 rearrangement in a 50-year-old male, demonstrating an unusual immunophenotypic and genetic profile reminiscent of LBCL-IRF4-R. Molecular analysis revealed mutations in CREBBP, KMT2D, IRF4, and CARD11, with previously unreported variants identified in IRF4 and CREBBP. This case broadens the spectrum of B-cell lymphomas associated with IRF4 rearrangement by demonstrating a small B-cell lymphoma with this genetic feature.