Mixed-phenotype acute leukemia (MPAL)

 

De novo acute leukemia containing separate populations of blasts of more than one lineage (bilineal or bilineage), or a single population of blasts co-expressing antigens of more than one lineage (biphenotypic)


Excludes:

  • Acute myeloid leukemia (AML) with recurrent translocations t(8;21), t(15;17) or inv(16)

  • Leukemias with FGFR1 mutations

  • Chronic myelogenous leukemia (CML) in blast crisis

  • Myelodysplastic syndrome (MDS) related AML and therapy related AML, even if they have MPAL immunophenotype

 

Score of 2 or more for each of two separate lineages (shown below)

                    MPAL T/Myeloid

  • Meets the diagnostic criteria for MPAL with both T and myeloid lineages without Ph+ and MLL rearrangement

  • More often in children, though in adults as well

  • Dimorphic populations, resembling lymphoblasts and myeloblasts, or a single population resembling ALL

  • Other commonly expressed T-lineage markers include CD2, CD7

  • Myeloid markers MPO, CD117, TdT, CD13 and CD33

  • T cell plus myeloid cases may have 2p13 translocations or other unrelated anomalies

CASE 1 MPAL T/M

Case 1 shows an example of MPAL with a single blast population (red). In this case, there is cytoplasmic CD3 expression, consistent with T lineage, in conjunction with myeloperoxidase, indicating myeloid lineage. also CD7, CD64, CD33 are positive. This was diagnosed as MPAL, T/myeloid. Figure 1B shows an example of MPAL with two distinct blast populations. The red population is identified as myeloid by the co-expression of two monocytic markers, CD14 (partially expressed) and CD64. The blue population is composed of B lymphoblasts, established by CD19 and CD79a expression. This was diagnosed as MPAL, B/myeloid.

CASE 2 MPAL T/M

Case 2 shows an example of MPAL with a single blast population (red). In this case, there is cytoplasmic CD3 expression, consistent with T lineage, in conjunction with myeloperoxidase, indicating myeloid lineage. also CD7, CD15, CD33,CD117 are positive. This was diagnosed as MPAL, T/myeloid.

CASE 3 MPAL T/M

Case 3 shows an example of MPAL with a blast population (red). In this case, there is cytoplasmic CD3 expression, consistent with T lineage, in conjunction with myeloperoxidase, indicating myeloid lineage. also CD7, CD5, CD33 are positive. This was diagnosed as MPAL, T/myeloid.

                             MPAL B/Myeloid

  • Meets the diagnostic criteria for MPAL with both B and myeloid lineages without Ph+ and MLL rearrangement

  • B/myeloid acute leukemia accounts for 1% of all leukemias

  • More common in adults but also seen in children

  • Morphology:Dimorphic populations, resembling lymphoblasts and myeloblasts, or a single population resembling ALL

  • Genetics:Multiple different cytogenetic changes have been demonstrated, however none is proven to be specific in this subtype

CASE 1 MPAL B/M

Case 1   shows an example of MPAL with two distinct blast populations (red). The red population is identified as myeloid by the co-expression of two myeloid markers MPO, CD33. The other  population is composed of B lymphoblasts, established by CD19, cCD22 and CD79a expression. This was diagnosed as MPAL, B/myeloid.

CASE 2 MPAL B/M

Case 2   shows an example of MPAL with two distinct blast populations  MPO and CCD79a positive populations(red). The MPO +population is identified as myeloid by the co-expression of two monocytic markers CD14, CD64 with CD13, CD33 and CD11b. The cCD79a  population is composed of B lymphoblasts, established by CD19, cCD22 and CD10 expression. This was diagnosed as MPAL, B/myeloid.

CASE 3 MPAL B/M

Case 3   shows an example of MPALcase with limited panel have  blast populations  MPO and CCD79a positive populations(red). The blast population is composed of B lymphoblasts, established by CD19, expression. This was diagnosed as MPAL, B/myeloid.

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          Vol 5,Issue 3,

                  2020

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