[Clinicopathological study of large B-cell lymphoma with IRF4 rearrangement]

Objective: To study the clinicopathological features of large B-cell lymphoma (LBCL) with IRF4 rearrangement. Methods: Seven cases of LBCL with IRF4 rearrangement collected at the First Affiliated Hospital of Nanjing Medical University from November 2018 to October 2019 were evaluated by hematoxylin and eosin staining, immunohistochemistry and fluorescence in situ hybridization detection. The relevant literature was reviewed. Results: Four tumors were located in the tonsils, 2 tumors in the lymphoid nodes and one tumor in the adenoid.The patients were 3 males and 4 females patients with a median age of 24 years (range, 6 to 39 years).Microscopically, entirely follicular pattern was present in one case, entirely diffuse pattern in 2 cases, and follicular and diffuse pattern in other 4 cases. The tumor cells were medium to large in size and showed the morphology of centroblasts or blastoid cells with irregular nuclei, brisk mitotic activity in 3 cases and starry sky in 2 cases. All of the cases were positive for CD20, PAX-5, bcl-6, and MUM1 and had a Ki-67 index>80%, while CD10 and bcl-2 were positive in 3 cases. IRF4 gene rearrangement was identified in all cases and bcl-6 gene rearrangement in 2 cases. All patients presented with localized disease with clinical stage Ⅰ or Ⅱ, except one with stage Ⅳ at presentation and a new lesion in the mediastinum developed 8 months later. Conclusions: LBCL with IRF4 rearrangement is a clinicopathologically distinct entity. The observations reveal a broader spectrum of morphology and biological behaviors. The relationship between clinical stage and prognosis needs to be determined in more cases.