W5L9 - Myeloproliferative Neoplasms & Myelodysplasia Flashcards
Myeloproliferative Neoplasms (MPN)
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
MPN Clinical
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
Chronic Myeloid Leukemia (CML)
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
Chronic Myeloid Leukemia - Pathophysiology
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
BCR/ABL Fusion Gene Product
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
Chronic Myeloid Leukemia - FBC Results in Chronic Phase
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
Chronic Myeloid Leukemia - Disease Progression
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
Chronic Myeloid Leukemia - Cytogenetics
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
Polycythaemia Vera (PV)
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
Polycythaemia Vera & Janus Kinase 2 Gene
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)
Polycythaemia Vera - Clinical Findings
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
Polycythaemia Vera - Diagnostic Criteria
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]
Essential Thrombocythaemia (ET)
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
Essential Thrombocythaemia - FBC Results
Thrombocytosis; >450 x 10^9/L
Anisocytosis of platelets; small to giant
Increased large, mature megakaryocytes in bone marrow
~50% microcytic, hypochromic anaemia
Primary Myelofibrosis
It is a myelofibrosis with myeloid metaplasia
Most cases 60-70 years of age
JAK2V617F in ~65% of cases
Prefibrotic & fibrotic phases
Primary Myelofibrosis - FBC Results (Fibrotic Phase)
Bone marrow variable cellularity
Left shift in granulocytes, <10% myeloblasts
Atypical megakaryocytes
Some microcytic, hypochromic anaemia
Prognosis of Patients with ET, PV or PMF
Median survival times:
- ~14 years for PV
- ~20 years for ET
- ~6 years for PMF
Chronic Myeloid Leukemia - Further Tests
Bone marrow studies - shows marked hypercellular marrow - myeloid proliferation Cytogenetics - chromosome analysis of Philadelphia chromosome FISH - confirms fusion of BCR/ABL gene
Myelodysplastic Syndromes
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
Types of Myelodysplastic Syndromes
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
Myelodysplastic Syndromes - Bone Marrow
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
Recurrent Mutations & Karyotypic Abnormalities in MDS
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
MDS Classification
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
Infections with MDS
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
Chronic Myelomonocytic Leukemia (CMML)
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
Chronic Myelomonocytic Leukemia Subcategories
CMML-1 - < 5% blasts in PB - < 10% blasts in BM CMML-2 - 5-19% blasts in PB - 10-19% blasts in BM
