Mixed-phenotype acute leukemia, T/megakaryoblastic: does it really exist?

We report the clinical presentation, diagnostic profile, and disease course of MPAL cases with a biphenotypic pattern consistent with T/megakaryoblastic lineage which is not yet defined in WHO classification. These cases were phenotyped using 8-color flow cytometry (BD FACS CANTO-II) using an extensive panel of markers. Interphase fluorescence in situ hybridization (FISH) was done using dual color dual fusion probes forBCR::ABL1,RUNX1::RUNX1T1, andETV6::RUNX1, whileMLL andCBFB gene rearrangement was tested by break-apart probes. Karyotyping was performed using the conventional GTG-banding technique. Both FISH and karyotyping were analyzed by the automated cell imaging system Leica Biosystems, using Cytovision MB8. The cases presented here satisfy the criteria for both T-lineage assignment (cyCD3 intensity reaches that of normal T-lymphocytes) and acute megakaryoblastic leukemia ( ≥ 1 megakaryocytic marker in >  50% blasts) and thus represent the first documented examples of this unusual entity from Pakistan. It is crucial to report these cases to gather more data about clinical presentation, diagnostic profile, and disease course. Additionally, the reported cases highlight the limitations of existing cl assifications which do not address rare subtypes. More importantly, T/megakaryoblastic MPAL needs to be included in the WHO classification as a separate entity.
Source: Journal of Hematopathology - Category: Pathology Source Type: research