TY - JOUR T1 - Tonsillar follicular large B-cell lymphoma with <em>IRF4</em> rearrangement causing sleep apnoea JF - Journal of Clinical Pathology JO - J Clin Pathol SP - 120 LP - 120 DO - 10.1136/jclinpath-2019-205915 VL - 73 IS - 2 AU - Yu-Ting Yu AU - Seiji Sakata AU - Kengo Takeuchi AU - L Jeffrey Medeiros AU - Kung-Chao Chang Y1 - 2020/02/01 UR - http://jcp.bmj.com/content/73/2/120.abstract N2 - An 8-year-old boy, without underlying disease, presented to the otolaryngologist with sleep apnoea and snoring. Physical examination showed bilateral tonsillar and adenoid hypertrophies and he underwent bilateral tonsillectomy and adenoidectomy. Review the high quality, interactive digital Aperio slide at http://virtualacp.com/JCPCases/jclinpath-2019-205915/ and consider your diagnosis.Follicular hyperplasia.Paediatric-type follicular lymphoma.Conventional follicular lymphoma.CD10-MUM1+follicular lymphoma.Large B cell lymphoma with IRF4 rearrangement.Pathologically, the follicles in the tonsils are numerous but only a subset is arranged in a back-to-back pattern (online supplementary figure S1). No abnormal follicle is found in the adenoid. These abnormal follicles show attenuated mantle zones, loss of polarity and starry-sky appearance (figure 1A), and are composed predominantly of medium-sized blasts (figure 1A, inset). Immunohistochemically, the cells in the abnormal follicles are positive for CD20, BCL-6 (figure 1B), BCL-2 (figure 1C) and MUM1/IRF4 (figure 1D) with a Ki-67 proliferative index of 20% to 30% (figure 1E). CD10 is however negative. An initial impression of paediatric-type follicular lymphoma was considered but the strong expression of MUM1/IRF4 suggests the alternative entity ─ follicular form of large B-cell lymphoma with IRF4 rearrangement.1 We, thus, performed a detailed fluorescence in situ hybridisation study using three-colour probes of mixed 6p25.3 region (IRF4) dual colour split … ER -