Application of 2016 WHO classification in the diagnosis of paediatric high-grade MYC -negative mature B-cell lymphoma with Burkitt-like morphological features.

Aims Historically, there has been no consensus on the diagnostic classification of high-grade B-cell lymphoma (HGBCL) with morphological features of Burkitt lymphoma (BL) but noMYCgene rearrangement (MYC-negative). The 2016 WHO classification of tumours of haematopoietic and lymphoid tissues has shed some light on this field with the modification of the grey-zone lymphoma with features intermediate between BL and diffuse large B-cell lymphoma, and the creation of several new entities. The aim of this study was to investigate how the revised WHO classification affects our practice in diagnosing these lymphomas in children. Methods We retrospectively reviewed cases of mature HGBCL diagnosed at our hospital between 2015 and 2018. Results Among 14 mature HGBCL cases with BL morphological features, 11 showedMYCrearrangement consistent with BL and 3 wereMYC-negative. TwoMYC-negative cases showed regions of 11q gain and loss by microarray consistent with Burkitt-like lymphoma with 11q aberration (BLL-11q). The thirdMYC-negative case showed diffuse and strong MUM1 expression, translocation involving 6p25 by chromosome analysis andIRF4rearrangement by fluorescence in situ hybridisation analysis consistent with large B-cell lymphoma withIRF4rearrangement (LBL-IRF4). All patients were treated according to applicable chemotherapeutic protocols and achieved remission. Conclusions BLL-11q and LBL-IRF4, two newly defined entities, should be considered in paediatricMYC-negative mature HGBCL cases. Accurate diagnosis needs careful histopathological examination and proper cytogenetic testing. Since they have unique cytogenetic features, specific treatments for them may emerge in the future. Therefore, accurate diagnosis based on the 2016 WHO classification is clinically significant.