[Large B-cell lymphoma with IRF4 rearrangement: six case reports and a literature review].

Objective: To study the clinical, histopathological, and genetic features of large B-cell lymphoma (LBCL) with IRF4 rearrangement. Methods: Six patients presenting at our center between December 2017 and October 2021 were evaluated by pathological examination, fluorescence in situ hybridization, and next-generation sequencing. The relevant literature was reviewed. Results: ①The study sample included three males and three females with a median age of 33 years. Three tumors were in the tonsils, two in the lymphoid nodes, and one in the dorsal lump. All patients were treated using the RCDOP (rituximab, cyclophosphamide, liposomal doxorubicin, vincristine, prednisone) regimen. All of them were alive at the time of follow-up in November 2021. ②Microscopic examination showed an entirely follicular pattern in one case and an entirely diffused pattern in 5 cases. The tumor cells were medium to large, and most of the lesions were dilatative with brisk mitotic activity (n=five cases) and no starry sky pattern (n=6 cases) . ③Four cases exhibited a GCB phenotype, and the other two exhibited a non-GCB phenotype. All of the cases were positive for CD20, PAX-5, MUM, and BCL6, and negative for CD5. Moreover, CD10, BCL2, and c-MYC were positive in 4, 3, and 2 cases, respectively.④IRF4 gene rearrangement was identified in all cases, BCL6 gene rearrangement was detected in 5 cases, and 2 cases were positive. BCL2 and MYC gene rearrangement were performed in 5 cases, all negative. ⑤Three paraffin tissue samples were used for next-generation sequencing, and lymphoma-related gene mutations such as IRF4, TP53, IGLL5, and MYD88 were detected in 3 cases. Conclusions: LBCL with IRF4 rearrangement is a rare entity with unique clinical, pathological, and genetic characteristics. This entity's pathogenesis, treatment options, and long-term prognosis still need to be explored further.