AML with Recurrent Genetic Abnormalities Flashcards
What specific gene mutations are a category
in the WHO for AML ?
- mutated NMP1
- biallelic CEBPA mutation
- mutated RUNX1 (provisional entity)
* Note: there are other mutations, FLT3-ITD and KIT mutations are common and are prognostic.
What is the definition of
AML with t(8;21)
RUNX1-RUNX1T1?
- defined by the fusion
- shows predominantly neutrophilic maturation
- large myeloblasts with basophilic cytoplasm and azurophilic granules
- high rates of complete remission and favorable long-term outcome
What is the epidemiology and the
clinical features of AML with t(8;21) ?
- about 1-5% of all AMLs
- can present with a myeloid sarcoma
- if that is the case then the bone marrow blasts may be low in number
What are some key morphologic
features of AML with t(8;21) ?
- large blasts with deep basophilic cytoplasm and numerous azurophilic granules and perinuclear hofs
- granules may be pseudo-Chediak Higashi like
- may also see some smaller blasts predominantly in the peripheral blood
- single, long tapered Auer rods
- may be seen in neutrophils as well
- Neutrophils with variable dysplasia
- hyposegmentation
- abnormal cytoplasmic granulation ( homogeneous pink)
- IMP:
- dysplasia in other cell lines is uncommon
What is common about the other
cell lines in AML with t(8;21) ?
- no significant dysplasia of the erythroid or megakaryocytes
- a monocytic component is usually minimal or absent
- eosinophil precursors are frequently increased but different from the inv(16) ones
- basophils and mast cells can be increased
- concurrent mastocytosis is seen in some cases
What is the immunophenotype of
AML with t(8;21) ?
- high intensity expression of CD34, HLA-DR, MPO and CD13
- relatively weak expression of CD33
- neutrophilic differentiation can be seen:
- positive for CD15 and/or CD65
- maturation asynchrony can sometimes be seen:
- coexpression of CD34 and CD15
- Other Key Markers positive:
- CD19, Pax-5 and CD79a
- TdT- weak expression
- CD56 (sometimes)- adverse prognostic significance
- may be due to KIT mutations in these cases
What is the genetic profile of
AML with t(8;21) ?
- core binding factor genes involved
- essential for hematopoiesis
- 70% of cases show additional chromosome abnormalities and mutations
- loss of sex chromosome or del 9q are most common
- KIT mutations occur in 20-30%
- KRAS and NRAS occur in 30% of pediatric and 10-20% adult cases
What is the prognosis of AML
with t(8;21) ?
- associated with high rate of remission when treated with high-dose Cytarabine
- and long-term disease free survival
- Adverse prognostic factors
- KIT mutations
- CD56 expression
What is the definition of AML
with inv(16) or t(16;16)
CBFB-MYH11 ?
- shows monocytic and granulocytic differentiation
- abnormal eosinophil component
What are the epidemiology and
clinical features of AML
with inv(16) ?
- represents 5-8% of younger patients with AML
- lower frequency in adults
- myeloid sarcoma may be initial or relapse presentation
- significantly higher WBC count
What are the microscopic findings
of AML with inv(16) ?
- usually AML with monocytic features
- Abnormal eosinophils
- without significant maturation arrest
- promyelocyte and myelocyte stage with large, basophilic granules (EOS-BASO)
- mature eosinophils sometimes show hyposegmentation
- sometimes can be difficult to find
- Auer rods
- Neutrophils are decreased
What is an unusual cytochemistry finding
in AML with inv(16) ?
- napthol AS-D chloracetate esterase
- normally negative in normal eosinophils
- faintly positive in the abnormal eosinophils in this AML
What is the immunophenotype of
AML with inv(16) ?
- complex immunophenotype with multiple blast populations
- Immature blasts
- CD34 and CD117 high expression
- Granulocytic lineage
- CD13, CD33, CD15, CD65 and MPO
- Monocytic lineage
- CD14, CD4, CD11b, CD11c, CD64, CD36 and lysozyme
- Other markers often positive
- CD2
- non-specific
What is the genetic profile of
AML with inv(16) ?
- inv(16) is the most common and t(16;16) is rarely seen
- both lead to a fusion of CBFB to MYH11
- conventional cytogenetics
- inv(16) is very subtle
- FISH and RT-PCR may be necessary
- FISH:
- fusion is normal
- break apart shows the split CBFB
- FISH:
What are frequent secondar genetic
alterations in AML with inv(16)?
- 40% of cases have secondary genetic alterations (most common below)
- gains of chromsome 22 and 8 (10-15% of cases)
- IMP: Trisomy 22 is fairly specific for inv(16)
- gain of chromsome 21 and del 7q
- gains of chromsome 22 and 8 (10-15% of cases)
- secondary gene mutations are very common
- KIT, NRAS, KRAS, FLT3
- ASXL2 (common in t(8;21)) but not common in inv(16)
What are the prognostic and predictive factors
in AML with inv(16) ?
- high rate of complete remission and favorable overall survival
- when treated with high dose cytarabine
- KIT mutations (especially exon 8) have higher risk of relapse and worse survival
- but still not as significant as AML with t(8;21)
- Gain of chromosome 22
- frequently seen associated with an improved outcome
- Worse outcome:
- older age, elevated WBC
- FLT3 mutations (esp. TKD)
- trisomy 8
What is the definition of AML
with t(15;17) ?
- PML-RARA
- abnormal promyelocytes predominate
- hypergranular (typical)
- hypogranular (or microgranular)
What is the epidmiology and clinical features
of APL ?
- accounts for 5-8% of all AML
- often in younger patients with lower frequency in elderly patients
- often associated with DIC and increased fibrinolysis
- microgranular
- very high WBC which is different from the typical kind
What are the microscopic findings of
the hypergranular (classic) type of APL ?
- abnormal promyelocytes are kidney shaped or bilobed
- cytoplasm has densely packed granules and auer rods (bright pink or purple)
- myeloblasts with single Auer rods may also be seen
- auer rods are larger in APL compared to other AMLs and have a periodicity of 250 nm compared to 6-20 for the others
- hypergranular APL
- usually presents with very low WBC
What are the microscopic findings of
the hypogranular variant of APL ?
- generally presents with a high WBC
- promyelocytes have a bilobed nucleus and a paucity of cytoplasmic granules
- can mimic a monocytic leukemia
- rare Auer rods can be found
- at relapse (after treatment with tretinoin) the cytoplasm can be deeply basophilic
- bone marrow is usually hypercellular
What are the cytochemical findings in APL ?
- MPO is strongly positive in both the hypergranular and microgranular variants
- helpful in differentiating from monocytes
- Non-specific esterase
- weakly positive in ~25% of cases
What is the characteristic immunophenotype
of APL ?
- Hypergranular variant
- low or absent : CD34, HLA-DR
- positive: CD11a, CD11b, CD117 (can be weak), bright CD33, CD64, and heterogeneous CD13
- negative for granulocytic markers: CD15 and CD65
- Microgranular variant
- some CD34 positivity and CD2 positive
- CD11c also positive
- CD11b and CD11c can be upregulated after treatment
- CD2 expression
- associated with FLT3-ITD
- CD56 - positive in 10% of cases
- associated with worse outcome
What is the genetic profile of
APL ?
- RARA gene (chromosome 17) fuses with PML (chromsome 15)
- complex variant translocations are also seen, must know
- can have submicroscopic insertions of the PML-RARA gene into different chromsomes
- considered cryptic or masked genes
- can have submicroscopic insertions of the PML-RARA gene into different chromsomes
- Secondary cytogenetic alterations (40% of cases)
- gain of chromsome 8 most frequent
- FLT3-ITD and FLT3-TKD (30-40% of cases)
- more often microgranular variant (high WBC count)
- involve the bcr3 breakpoint of PML
What are the key variant translocations
seen in APL ?
- Variant partners
- ZBTB16 (previously called PLZF) - 11q23.2
- NUMA1 - 11q13.4
- NPM1- 5q35.1
- STAT5B - 17q21.2
- in general most of the variants have APL morphology, with some exceptions
What is the morphology of variant APL
t(11;17) ZBTB16-RARA ?
- predominance of cells with regular nuclei and many granules
- usually an absence of Auer rods
- increased number of plegeroid neutrophils
- strong MPO activity
Which variant APL translocations are
resistant to ATRA ?
- ZBTB16-RARA
- STAT5B-RARA
What are the prognostic and predictive
factors of APL ?
- very sensitive to ATRA and arsenic trioxide
- allows the cells to differentiate
- best prognosis of all AML subtypes if treated appropriately
- anthracycline is added for high risk patients
What is the definition, epidemiology
and clinical features of AML t(9;11)
KMT2A-MLLT3 ?
- usually associated with monocytic features
- IMP:
- more common in children
- only 2% of adult AMLs
- can present with DIC or myeloid sarcoma
What is the immunophenotype if
AML with t(9;11) ?
- in children:
- positive: CD33, CD65, CD4 and HLA-DR
- low expression of: CD13, CD34, and CD14
- in adults:
- positive: monocytic markers
- CD14, CD4, CD11b, CD11c, CD64, CD36 and lysozyme
- variable to no expression of markers indicative of immaturity
- CD34, CD117, and CD56
- positive: monocytic markers
What is the genetic profile of
AML with t(9;11) ?
- KMT2A protein
- histone methyltransferase that assembles protein complexes
- most common is t(9;11)
- secondary cytogenetic abnormalities are frequent
- most common: gain of chromsome 8
- usually MECOM negative
- MECOM (aka EVI1) is reported in 40% of cases
- these cases seem to behave differently than MECOM-negative ones
- most common: gain of chromsome 8
What are the variant KMT2A translocations
in acute leukemia ?
- there are >120 translocations involving KMT2A
- review this section p. 137
- some KMT2A translocations are subtle
- may need FISH or other molecular studies to identify the variants
- MECOM overexpression is frequently seen
What are the prognostic and predictive factors
for AML with t(9;11) ?
- AML with this translocation has an intermediate survival
- better than the other KMT2A translocations
- MECOM
- if present portends a poor prognosis
What is the definition of AML with
t(6;9) DEK-NUP214 ?
- AML with >20% blasts
- generally has monocytic features
- basophilia and multilineage dysplasia are frequent
What is the epidemiology and clinical features
of AML with t(6;9) DEK-NUP214 ?
- translocation is seen in 0.7-1.8% of AMLs
- seen in both kids (median age 14) and adults (35-44 years)
- usually present with:
- anemia and thrombocytopenia
- can present with pancytopenia
- IMP: generally the WBC is lower than most AMLs and may be barely above normal
What are the microscopic findings of
AML with t(6;9) ?
- blasts typically have features of other AMLs (except for APL and megakaryoblastic)
- generally myelomonocytic and with maturation
- Auer rods (~1/3 of cases)
- marrow and peripheral blood basophilia ~2% (up to 60% of cases)
- granulocytic and erythroid dysplasia
- ring sideroblasts in some cases
What are the immunophenotypic findings
of AML with t(6;9) ?
- non-specific myeloid phenotype
- MPO, CD9, CD13, CD33, CD38, CD123 and HLA-DR
- most cases also positive for CD117 and CD34 and CD15
- some cases express: CD64 and TdT
- other lymphoid antigens are uncommon
- Basophils
- CD123, CD33 and CD38 +
- HLA-DR (-)
What are the genetic findings
in AML with t(6;9) ?
- t(6;9) creates a fusion protein
- acts as an aberrant transcription factor and alters nuclear transport by binding to soluble factors
- the sole clonal abnormality in most cases
- FLT3-ITD mutations are very common
- not the TKD mutations
What are the prognostic and predictive factors
of AML with t(6;9) ?
- generally a poor prognosis
- increased WBC and increased bone marrow blasts are most predictive of shorter overall survival
- despite the high numbers of FLT3-ITD
- does not appear to alter the OS
- may benefit from FLT3 inhibitors
What is the definition of AML with inv(3) or
t(3;3), GATA2-MECOM ?
- dereguated MECOM (also called EVI1) and GATA2 expression
- requires 20% peripheral blood or bone marrow blasts
- often associated with elevated platelet counts
What is the typical morphology of
AML with inv(3) or t(3;3)?
- increased dysplastic megakaryocytes
- unilobed or bilobed
- multinlineage dysplasia
What is the epidemiology of AML
with inv(3) or t(3;3) ?
- accounts for only 1-2% of AMLs
- occurs most commonly in adults
- no sex predilection
What are the clinical features
associated with AML with inv(3) or t(3;3) ?
- most present with anemia and thrombocytopenia
- 7-22% of cases can present with significant thrombocytosis
- hepatosplenomegaly may be present but lymphadenopathy should not occur
What are the morphologic features in the
peripheral blood of AML inv(3) ?
- hypogranular neutrophils
- can have pseudo-pelger huet cells as well
- peripheral blood blasts can also be seen
- RBC anomalies are usually mild
- no teardrop cells
- Giant and hypogranular platelets are common
- bare megakaryocytic nuclei can be seen
What are the morpologic features of
blasts in AML inv(3) ?
- they have variable morphologic and cytochemical features
- AML without maturation
- AML with maturation
- acute megakaryoblastic leukemia
- these three morphologies are the most common
What are the bone marrow findings for
AML with inv(3) ?
- multilineage dysplasia is frequent with dysplastic megakaryocytes being the most common finding (small, hypolobated forms)
- megas are usually also increased in number
- marrow eosinophils, basophils and mast cells can be increased in number
- fibrosis and cellularity are variable
What is the immunophenotype fo the blasts
in AML with inv(3) ?
- Positive:
- CD34, CD33, CD13, CD117 and HLA-DR
- Note: high CD34 expression is more often seen with inv(3) than with t(3;3)
- CD38
- CD7 (aberrant)- other lymphoid marker expression uncommon
- CD41 and CD61 (megakaryocyte markers) can occasionally be seen
- CD34, CD33, CD13, CD117 and HLA-DR
What is important about the genetic alterations
of AML with inv(3) or t(3;3) ?
- MECOM gene is on chromosome 3q26.2
- the genetic alterations reposition the GATA2 enhancer to activate MECOM expression
- IMP:
- MECOM overexpression is not specific to this AML it can be seen in other AMLs particularly therapy-related disease such as t(3;21) MECOM-RUNX1
What other genetic abnormalities can be seen
in AML with inv(3) ?
- secondary karyotypic abnormalities are frequent
- most common is monosomy 7 in 50% of cases
- second most common is del 5q and complex karyotypes
- secondary gene mutations are seen in almost all cases
- mutations activating RAS/receptor tyrosine kinase signalling pathways occur in 98%
- most common in descending order: NRAS, PTPN11, FLT3, KRAS, NF1, CBL, and KIT
- other common genes that are mutated: RUNX1, GATA2, and SF3B1 (usually associated with GATA2 mutation)
- mutations activating RAS/receptor tyrosine kinase signalling pathways occur in 98%
How is BCR-ABL1 positive CML with
inv(3) or t(3;3) best classified?
- it is best considered as accelarated or blast phase of CML and not AML
- presence of the inversion or translocation is indicative of progression
What are the prognostic and predictive factors
of AML with inv(3) or t(3;3) ?
- aggressive disease with short survival
- regardless of blast percentage:
- complex karyotype and additional monosomy 7 are associated with an even worse prognosis
What is the definition of AML with t(1;22)
RBM15-MKL1 ?
- AML that generally shows maturation in the megakaryocytic lineage
What is the epidemiology of AML
with t(1;22), RBM15-MKL1 ?
- uncommon abnormality in AML (<1%)
- most common in children with Trisomy 21
- female predominance
- can be congenital
What are the clinical features of
AML t(1;22) RBM15-MKL1 ?
- unique AML most often seen in children <3 years old
- most cases occur in the first 6 months of life
- present with:
- anemia and thrombocytopenia
- moderately elevated WBC
- organomegaly , particularly hepatosplenomegaly
What are the microscopic features of
AML with t(1;22)?
- the peripheral blood and bone marrow blasts are similar to those seen in acute megakaryoblastic leukemia
- small and large megakaryoblasts may be present and they may be admixed with more undifferentiated blast cells that resemble lymphoblasts
What is the morphology of the megakaryoblasts
seen in AML with t(1;22) ?
- medium to large in size
- round to slightly irregular and indented nucleus with fine reticular chromatin and 1-3 nucleoli
- cytoplasm is basophilic, often agranular with possible blebs or cytoplasmic projections
- micromegas are common but dysplastic features in the granulocytes and erythroids are not common
What are the other bone marrow
findings in AML with t(1;22) ?
- can be normocellular or hypercellular
- often there is dense fibrosis similar to that seen with metastatic tumors
- because of this the aspirate may be less helpful in getting 20% blasts on the differential count
What is a key cytochemical staining finding in
the megakaryoblasts of AML with t(1;22) ?
- the megakaryoblasts are negative for Sudan Black B and MPO
What is the immunophenotype of the
blasts in AML with t(1;22) ?
- express one or more of the platelet glycoproteins:
- CD41 (GP IIb/IIIa)
- CD61 (GP IIIa)
- CD42b (GP Ib)
- IMP: cytoplasmic staining for CD41 and CD61 are more specific and sensitive for megakaryocytic differentiation
- Positive for:
- CD13 and CD33
- CD36, not specific
- Negative for:
- CD45, CD34, and HLA-DR
- MPO, lymphoid markers and TdT
What are the genetics of AML
with t(1;22) ?
- should have the translocation or at least evidence of RBMK15-MKL1 gene fusion
- generally this is the sole karyotypic abnormality
- RBM15
- encodes RNA recognition motifs and split-end (spen) paralogue and orthologue C-terminal domains
- MKL1
- encodes a DNA-binding motif involved in chromatin organization
- Fusion gene
- may modulate chromatin organization
- HOX-induced differentiation and extracellular signalling pathways
What are the prognostic and predictive factors
for AML t(1;22)?
- most studies have shown this to be a high risk disease as compared to acute megakaryocytic leukemia without the t(1;22)
