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 no MYC gene 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 showed MYC rearrangement consistent with BL and 3 were MYC-negative. Two MYC-negative cases showed regions of 11q gain and loss by microarray consistent with Burkitt-like lymphoma with 11q aberration (BLL-11q). The third MYC-negative case showed diffuse and strong MUM1 expression, translocation involving 6p25 by chromosome analysis and IRF4 rearrangement by fluorescence in situ hybridisation analysis consistent with large B-cell lymphoma with IRF4 rearrangement (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 paediatric MYC-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.