[Clinicopathological and molecular genetic features of large B-cell lymphoma with IRF4 gene rearrangements involving the head and neck region in adults].

Objective: To investigate the clinicopathological features and molecular genetics of large B-cell lymphoma with IRF4 gene rearrangements (LBL-IRF4) involving the head and neck region in adults. Methods: The clinicopathological and molecular genetics features of LBL-IRF4 in adults diagnosed at the First Affiliated Hospital of Zhengzhou University between January 2016 and December 2024 were analyzed using immunohistochemistry and fluorescence in situ hybridization (FISH). Clinical information was also collected and analyzed. Results: Seventeen cases were reviewed. There were 5 male and 12 female patients, aged 19 to 68 years, with media age of 42.0(21.0,61.5) years. All patients presented with head and neck lesions, especially Waldeyer's ring and cervical lymphadenopathy (15/17). No bone marrow involvement was detected in any of the patients while most of them were at the Ann Arbor stage Ⅰ-Ⅱ (16/17). Morphologically, 11 cases had a diffuse growth pattern, and 6 cases had a follicular/diffuse growth pattern, exhibited medium to large lymphoid cells. Two cases showed a "starry sky" appearance, and 4 cases exhibited coagulative necrosis. Tumor cells were positive for CD20 and CD79a. CD10 was positive in 13 cases (13/17) while bcl-2 was positive in 12 cases (12/17). Bcl-6 and MUM-1 were positive in all cases. CD5 was expressed in 5 cases (5/17). All cases were EBV-negative (0/16). IRF4 rearrangement was identified in all cases. No breaks in MYC or bcl-2 were detected in any of the cases. Bcl-6 rearrangements were found in 8 cases (8/17) by FISH. All 17 patients received chemotherapy after the diagnosis. Sixteen patients at follow up were alive (1 case was lost to follow-up). Conclusions: LBL-IRF4 involving the head and neck in adults is not uncommon. Adult cases mimic their pediatric counterparts, showing similar morphological and immunohistochemical features. Some cases are CD5 positive and harbor bcl-6-rearrangement. Overall, it carries a favorable prognosis. Routine testing of IRF4 rearrangement is recommended for cases with the following characteristics: in the head and neck region, morphologically high-grade follicular lymphoma or diffuse large B-cell lymphoma with strong MUM-1 expression irrespective of patient age.