Aggressive B-cell non-Hodgkin lymphomas: a report of the lymphoma workshop of the 20th meeting of the European Association for Haematopathology

SOHO State of the Art Updates and Next Questions | High-Grade B-Cell Lymphomas: Pathologic and Molecular Classification and Therapeutic Implications

High-grade B-cell lymphomas (HGBLs) represent a diverse and aggressive group of neoplasms that lie at the intersection of diffuse large B-cell lymphoma (DLBCL) and Burkitt lymphoma (BL), characterized by unique molecular and clinical features. The recently published International Consensus Classification of Myeloid and Lymphoid Neoplasms (ICC) and the fifth edition WHO Classification of Hematolymphoid Tumors have refined the classification of HGBLs dividing them into subtypes based on clinical, morphologic, and molecular features, with subtle differences in terminology and entity characterization. These lymphomas present significant diagnostic challenges due to overlapping features with DLBCL and BL, and their aggressive clinical course necessitates tailored treatment strategies. Conventional therapies, such as R-CHOP, have demonstrated limited efficacy in these patients, prompting exploration of more intensive regimens and targeted therapies. The identification of molecular biomarkers, such as MYC, BCL2, and/or BCL6 rearrangements, as well as the emerging molecular high-grade (MHG) signature, holds promise for better understanding the pathogenesis of these lymphomas and improving prognostic stratification. Despite advances in classification, no clear consensus exists on optimal treatment approaches, and outcomes remain suboptimal, particularly in cases with isolated MYC translocations. This review aims to summarize the current pathologic and molecular classification of HGBLs, highlight the diagnostic challenges, and explore therapeutic implications, including potential future directions for treatment strategies and molecular-targeted therapies.

Cytogenetic and pathologic characterization of MYC-rearranged B-cell lymphomas in pediatric and young adult patients

MYC-rearranged B-cell lymphoma (BCL) in the pediatric/young adult (YA) age group differs substantially in disease composition from adult cohorts. However, data regarding the partner genes, concurrent rearrangements, and ultimate diagnoses in these patients is scarce compared to that in adult cohorts. We aimed to characterize the spectrum of MYC-rearranged (MYC-R) mature, aggressive BCL in the pediatric/YA population. A retrospective study of morphologic, immunophenotypic, and fluorescence in situ hybridization (FISH) results of patients age ≤ 30 years with suspected Burkitt lymphoma (BL), diffuse large B-cell lymphoma (DLBCL) or high-grade B-cell lymphoma (HGBCL), and a MYC-R by FISH between 2013-2022 was performed. Two-hundred fifty-eight cases (129 (50%) pediatric (< 18 years) and 129 (50%) YA (18-30 years)) were included. Most MYC-R BCL in pediatric (89%) and YA (66%) cases were BL. While double-hit (DH) cytogenetics (MYC with BCL2 and/or BCL6-R, HGBCL-DH) was rare in the pediatric population (2/129, 2%), HGBCL-DH increased with age and was identified in 17/129 (13%) of YA cases. Most HGBCL-DH had MYC and BCL6-R, while BCL2-R were rare in both groups (3/258, 1%). MYC-R without an IG partner was more common in the YA group (14/116 (12%) vs 2/128 (2%), p = 0.001). The pediatric to YA transition is characterized by decreasing frequency in BL and increasing genetic heterogeneity of MYC-R BCL, with emergence of DH-BCL with MYC and BCL6-R. FISH to evaluate for BCL2 and BCL6 rearrangements is likely not warranted in the pediatric population but should continue to be applied in YA BCL.