Table of Contents
Definition / general | Diagrams / tables | Prognosis and treatment | MPAL with t(9;22)(q34;q11.2); BCR-ABL1 | MPAL with t(v;11q23); MLL rearranged | Molecular / cytogenetics images | MPAL B/Myeloid, NOS | MPAL T/Myeloid, NOS Cite this page: Mihova D. Mixed phenotype. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/leukemiamixedpheno.html. Accessed June 2nd, 2023.
Definition / general
- 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
Criteria for biphenotypic leukemia:
- Score of 2 or more for each of two separate lineages (shown below)
Diagrams / tables
Contributed by Daniela Mihova, M.D.
The European Group
for the Immunological
Classification of Leukemias
(EGIL) scoring system
2008 WHO
classification of
acute leukemias of
ambiguous lineage
Prognosis and treatment
- Poor, overall survival of 18 months
- Young age, normal karyotype and ALL induction therapy are associated with favorable survival
- Ph+ is a predictor for poor prognosis
- Bone marrow transplantation should be considered in first remission
MPAL with t(9;22)(q34;q11.2); BCR-ABL1
- 20% of all MPAL
- Blasts with t(9;22)(q34;q11.2) translocation or BCR-ABL1 rearrangement (Ph+) without history of CML
- Majority in adults
- High WBC counts
- Most of the cases B/myeloid phenotype
- Rare T/myeloid, B and T lineage, or trilineage leukemias
Morphology:
- Many cases show a dimorphic blast population, one resembling myeloblasts and the other lymphoblasts
Cytogenetic abnormalities:
- Conventional karyotyping for t(9;22), FISH or PCR for BCR-ABL1 translocation
- Additional complex karyotypes
- Ph+ is a poor prognostic factor for MPAL with a reported median survival of 8 months
- Worse than patients of all other types of MPAL
MPAL with t(v;11q23); MLL rearranged
- Meeting the diagnostic criteria for MPAL with blasts bearing a translocation involving the 11q23 breakpoint (MLL gene)
- MPAL with MLL rearranged rare
- More often seen in children and relatively common in infancy
- High WBC counts
- Poor prognosis
- Dimorphic blast population with one resembling monoblasts and the other resembling lymphoblasts
- Lymphoblast population often shows a CD19+, CD10- B precursor immunophenotype, frequently CD15+
- Expression of other B markers usually weak
- Translocations involving MLL gene include t(4;11)(q21;q23), t(11;19)(q23;p13) and t(9;11)(p22;q23)
- Cases with chromosome 11q23 deletion should not be classified in this category
Molecular / cytogenetics images
AFIP images
t(4;11)(q21;23) in bilineal leukemia
MPAL B/Myeloid, NOS
- 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
MPAL T/Myeloid, NOS
- 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 (Leukemia 2007;21:2264)
