The diagnostic gray zone between Burkitt lymphoma and diffuse large B-cell lymphoma is also a gray zone of the mutational spectrum

摘要

The current WHO classification recognizes the existence ofaggressive B-cell lymphomas that share morphological, immunophenotypic and gene expression profile-based features intermediate between Burkitt lymphomas (BLs) and diffuse largeB-cell lymphomas (DLBCLs) and created the provisional categoryof ‘B-cell lymphoma, unclassifiable, with features intermediatebetween BL and DLBCL (BCL-U)’.1 From a clinical perspective,however, the introduction of the diagnostic BCL-U categoryappears problematic, because current therapeutic conceptsdiffer significantly between BL and DLBCL. Moreover, manypatients with BCL-U have a dismal prognosis. Translocations ofthe MYC oncogene are common in BCL-U, usually in the contextof a complex genetic background, and 35–50% of BCL-Ulymphomas, next to MYC aberrations, harbor additional translocations involving BCL2 and/or BCL6. These cases are referred toas ‘double hit’/’triple hit’ (DH/TH) lymphomas. However, neitherMYC translocations nor a ‘double hit’/triple hit’ genetic constellation are unifying genetic features of BCL-U, as ~ 10% of DLBCLcarry MYC translocations or show DH/TH features as well.1Nonetheless, according to current concepts, these B-cell nonHodgkin lymphomas (B-NHLs) are categorized as DLBCL on thebasis of their morphological features, although there is evidencethat these genetic alterations may predict inferior outcomeamongst DLBCL patients.