Analysis of clinicopathological and cytogenetic differences between B-lymphoblastic lymphoma and B-lymphoblastic leukemia in childhood.

Although considered the same disease by 2016 WHO Classification, B-ALL and B-LBL show different clinicobiologic behavior, with B-ALL manifesting as disseminated disease and B-LBL as a localized mass. Distinction between the two is based on an arbitrary cutoff of 25% bone marrow involvement. We reviewed clinical, immunophenotypic, and cytogenetic data in B-lymphoblastic neoplasms of childhood to explain the differences. Performing a retrospective review of 126 cases of B-ALL and 18 cases of B-LBL in patients ≤18 years, revealed the following significant differences: younger age of presentation for leukemia; increased cytogenetic abnormalities in leukemia than lymphoma, specifically increased recurrent genetic abnormalities, with the exception of ploidy aberrancy; and the observation that unfavorable recurrent genetic abnormalities occurred in B-ALL and only favorable abnormalities in B-LBL. Down syndrome presented with leukemia only. Findings demonstrated that pediatric B-ALL and B-LBL exhibit dissimilar genomic profiles, suggesting possible differences in pathogenesis between the two closely-related neoplasms.