W5L9 - Myeloproliferative Neoplasms & Myelodysplasia

Question 1

Myeloproliferative Neoplasms (MPN)

Answer 1

A.k.a myeloproliferative disorders (MPD)
Clonal stem cell disorders of haematopoietic cells including:
- chronic myeloid leukaemia
- polycythaemia vera
- primary Myelofibrosis
- essential thrombocythaemia
- others…
Typically result in increased production of cells & increased [] of cells in the peripheral blood

Question 2

MPN Clinical

Answer 2

Characterised by:

• increased myeloid proliferation
• increased [peripheral blood]
• increased bone marrow haematopoiesis (medullary)
• extra-medullary haematopoiesis => organomegaly (e.g. splenomegaly)
• bone marrow fibrosis (eventual)
• spontaneous transformation into acute leukaemia
• increased risk of thrombotic & haemorrhagic events

Question 3

Chronic Myeloid Leukemia (CML)

Answer 3

Neoplasm of granulocytes
The main symptoms & signs at presentation are fatigue, anaemia, splenomegaly, abdominal discomfort & episodes of infections
However, a significant proportion of patients are asymptomatic
CML is usually diagnosed in chronic phase
Males have an increased incidence of CML at a ratio of 1.3–1.5:1.0
The median age at presentation in Australia 55 years

Question 4

Chronic Myeloid Leukemia - Pathophysiology

Answer 4

CML is caused by the formation of Philadelphia chromosome (Ph1)
- translocation between chromosomes 9 & 22 (t9:22)
Found in > 95% of CML
Leads to formation of fusion between…
- BCR: breakpoint cluster region protein
- ABL : abelson murine leukemia viral oncogene homolog 1
Leads to the formation of BCR-ABL1 fusion gene
BCR-ABL1+ is an important diagnostic criteria for CML

Question 5

BCR/ABL Fusion Gene Product

Answer 5

Multiple oncogenic effects include:

• ABL binding site causes dysregulation of cell adhesion and/or migration
• oxidative stress, DNA lesions & disrupted DNA repair
• activate multiple signal pathways resulting in the upregulation of cell proliferation, differentiation & survival
• down regulation of apoptosis
• activates Ras, JAK-STAT, PI-3 kinase pathways => same stimulated by haematopoietic growth factors in normal progenitors

Question 6

Chronic Myeloid Leukemia - FBC Results in Chronic Phase

Answer 6

WBC 12-1000 x 10^9/L
Median ~100 x 10^9/L
~50 mature neutrophils
<2% blasts
Eosinophilia, basophilia also common
Bone marrow < 5% blasts

Question 7

Chronic Myeloid Leukemia - Disease Progression

Answer 7

Disease progression is characterised by the blast cell count
Accelerated phase
- 10-19% blasts in PB or BM
- > 20% more basophils in PB
Blast phase
- > 20% blasts in the PB
- extramedullary accumulation of blasts
- blast phenotype can be myeloid or lymphoid or, in rare cases, both
- myeloid blast is predominantly observed (on a 2:1 ratio) compared with lymphoid BC

Question 8

Chronic Myeloid Leukemia - Cytogenetics

Answer 8

80-90% of patients with CML in chronic phase show the Philadelphia chromosome
The rest display additional cytogenetic aberrations (ACAs)
Percentage of patients with ACAs is relatively low in chronic phase but increases during the course of disease to 30% in accelerated phase and 60-80% in blast crisis

Question 9

Polycythaemia Vera (PV)

Answer 9

Well differentiated haematopoietic neoplasia of RBC
Myeloproliferative neoplasm
Excess production of RBC => ↑ RBC mass
Three phases:
- pre polycythaemic
- overt polycythaemic
- post polycythaemic phase (post-polycythaemic myelofibrosis & myeloid metaplasia => anaemia)
Most cases 50-60 years of age

Question 10

Polycythaemia Vera & Janus Kinase 2 Gene

Answer 10

JAK2 mediates signaling of:
- receptors with tyrosine kinase activity e.g. KIT gene coding for stem cell factor
JAK2V617F point mutation in position 1849 of exon 14 of the Janus kinase gene = G→T (Valine → Phenylalanine)
Identified in ~96% of cases of PV
JAK2V617F also occurs in essential thrombocytothaemia and primary myelofibrosis, with respective mutational frequencies of 55% and 65%
An additional mutation has been identified in exon 12 of JAK2 ~3% of PV patients (who did not have a JAK2 V617F mutation)

Question 11

Polycythaemia Vera - Clinical Findings

Answer 11

FBC
- increased RBC mass (Hb, haematocrit, RBC)
- ~50% thrombocytosis; 450-800 x 10^9/L
- ~66% granulocytosis; 12.0-25.0 x 10^9/L
Bone marrow
- increased erythropoiesis
- increased numbers of megakaryocytes
- possible granulocytic hyperplasia
- in post-polycythaemic phase => myelofibrosis & myeloid metaplasia
Normal arterial p02
Low serum Epo concentration

Question 12

Polycythaemia Vera - Diagnostic Criteria

Answer 12

Require 3x major or 2x major+ 1x minor criteria for diagnosis
Major Criteria
- Hb > 165 g/L (male)/160 g/L (female)
- BM trilineage hyperplasia
- JAK2V617F/JAK2exon12 mutation
Minor Criteria
- decreased [Epo]

Question 13

Essential Thrombocythaemia (ET)

Answer 13

Myeloproliferative neoplasm
Well differentiated neoplasia of platelets/megakaryocytes
Classification based of [platelet], bone marrow characteristics, JAK2 mutation (~55%), presence/absence of defined other mutations
Most cases 50-60 years of age; some 20-40 years old

Question 14

Essential Thrombocythaemia - FBC Results

Answer 14

Thrombocytosis; >450 x 10^9/L
Anisocytosis of platelets; small to giant
Increased large, mature megakaryocytes in bone marrow
~50% microcytic, hypochromic anaemia

Question 15

Primary Myelofibrosis

Answer 15

It is a myelofibrosis with myeloid metaplasia
Most cases 60-70 years of age
JAK2V617F in ~65% of cases
Prefibrotic & fibrotic phases

Question 16

Primary Myelofibrosis - FBC Results (Fibrotic Phase)

Answer 16

Bone marrow variable cellularity
Left shift in granulocytes, <10% myeloblasts
Atypical megakaryocytes
Some microcytic, hypochromic anaemia

Question 17

Prognosis of Patients with ET, PV or PMF

Answer 17

Median survival times:

• ~14 years for PV
• ~20 years for ET
• ~6 years for PMF

Question 18

Chronic Myeloid Leukemia - Further Tests

Answer 18

Bone marrow studies
- shows marked hypercellular marrow 
- myeloid proliferation
Cytogenetics
- chromosome analysis of Philadelphia chromosome
FISH
- confirms fusion of BCR/ABL gene

Question 19

Myelodysplastic Syndromes

Answer 19

Group of clonal bone marrow neoplasms characterised by simultaneous proliferation & apoptosis of cells in BM => ineffective haematopoiesis
Most cases occur in elderly patients
One or more cell line may be affected
Characteristically dysplasia is evident => abnormal morphology
May be
- primary = arising de novo
- secondary (following chemotherapy or radiation therapy)
May progress to AML

Question 20

Types of Myelodysplastic Syndromes

Answer 20

Most types designated with ‘MDS’
Ringed sideroblasts indicate Fe deposition in mitochondria following ineffective Hb production
Note the number of cell lines affected
Categories:
- MDS with single lineage dysplasia
- MDS with ring sideroblasts (MDSRS)
- MDS-RS and single lineage dysplasia
- MDS-RS and multilineage dysplasia
- MDS with multilineage dysplasia
- MDS with excess blasts
- MDS with isolated del(5q)
- MDS, unclassifiable

Question 21

Myelodysplastic Syndromes - Bone Marrow

Answer 21

Should include Romanowsky stain & Perl’s Prussian Blue stain
Features of bone marrow include:
1. RBCs
- megaloblastoid features
- ringed sideroblasts
- nuclear abnormalities
- marked anisocytosis
2. Granulocytes
- few, large granules
- nuclear abnormalities
3. Megakaryocytes/platelets
- wide range size
- nuclear abnormalities
4. Presence of blasts

Question 22

Recurrent Mutations & Karyotypic Abnormalities in MDS

Answer 22

Only approximately 10% of patients lack mutations in any of the common recurrently mutated genes
Targeted sequencing of a limited number of genes can detect mutations in up to 90% of MDS patients
The most commonly mutated genes in MDS are SF3B1, TET2, SRSF2, ASXL1, DNMT3A, RUNX1, U2AF1, TP53, and EZH2
These fit into the following categories:
- ∼50% of patients have a mutated splicing factors (SF)
- ∼50% of patients have a mutated epigenetic regulator (ER)
- ~25% of patients have mutations of genes in both groups

Question 23

MDS Classification

Answer 23

Characterised according to cell line affected by dysplasia
Also consequential cytopenia
Cytopenia defined as:
- anaemia < 100g/L
- platelets < 100 x10^9/L
- neutrophils < 1.8 x10^9/L
May be single lineage, bilineage, trilineage

Question 24

Infections with MDS

Answer 24

Patients with myelodysplastic syndromes are associated with a risk of severe infections
Neutropenia is the main predisposing factor
Several other immune defects have been reported
- including impaired neutrophil function and B-, T- & NK-cell defects

Question 25

Chronic Myelomonocytic Leukemia (CMML)

Answer 25

Most cases >50 years of age
FBC
- Persistent monocytosis; > 1 x 10^9/L
- morphology typically normal; <20% blasts in blood
- ~50% of patients ↑ WBC (myeloproliferative)
Cytogenetics
- no Ph chromosome or BCR/ABL fusion gene
- nonspecific cytogenetic abnormality in ~20-40% of patients
Bone Marrow
- dysplastic features in ≥ 1 myeloid lineages
- granulocytic proliferation, dysgranulopoiesis, dyserythropoiesis, megaloblastoid, ringed sideroblasts
- micromegakaryocytes in 80% of patients
Median survival time ~20-40 months
15-30% convert to acute leukemia

Question 26

Chronic Myelomonocytic Leukemia Subcategories

Answer 26

CMML-1
- < 5% blasts in PB
- < 10% blasts in BM
CMML-2
- 5-19% blasts in PB
- 10-19% blasts in BM