CD5+ Large B cell lymphoma with IRF4 rearrangement: case report and review of the literature

Abstract Introduction/Objective Large B cell lymphoma with IRF4 rearrangement was introduced as a diagnosis by WHO in 2017. It is a rare entity that affects Waldeyer’s ring in mostly males, children and young adults. The lesional immunophenotype may be positive for CD10. FISH is positive for IRF4 rearrangement on chromosome 6p25.Among reported cases in the English literature only 6 cases have reported specifically CD5 being negative. We present review of the literature during years 2020-2024, and a case of large B cell lymphoma with IRF4 rearrangement, specifically positive for CD5. Methods/Case Report The patient is a 5 years old male, since 2017 suffering from recurring ear infections with approximately 4-5 episodes of otitis media during every 6 months. In 2019 the patient’s mother reported snoring, constant sore throat, bad breath for 2 years. On physical examination the left tonsil appeared enlarged; exudative tonsillitis was present. Later on, an asymmetric, firm mass in the location of the left tonsil with induration of the left palate was identified. CT scan showed mild asymmetric soft tissue thickening of the left aspect of the soft palate and left palatine tonsil. Mildly prominent left-sided levels IIa and IIb lymph nodes, measuring up to 1 cm were identified. H&E sections revealed an expansile proliferation of neoplastic cells, large with void to indented nuclei, vesicular chromatin, small nucleoli, visible cytoplasms. Frequent mitoses, apoptosis and individual cell necrosis were seen. Immunohistochemistry revealed CD20+ B cell neoplasm with high expression for MUM1 and high proliferation rate along with strong CD5+ and CD10-. By multicolor flow cytometric studies, an abnormal B cell population was found (40%) with increased forward scatter along with expression for CD5, CD19, CD20, CD22, CD45, CD79a (cytoplasmic), FMC7, (dim) lambda-restriction. Fluorescence In Situ Hybridization Study revealed IRF4 (DUSP22) rearrangement on chromosome 6p25. Results (if a Case Study enter NA) NA Conclusion We analyzed 24 cases reported in the English literature. The mean age of the patients is 7 years old. The majority are males (14/24 = 58%).The most common location is tonsil/ neck mass (15/24 = 62%).CD5 was negative in 6/24 cases.