Myeloproliferative Neoplasms - MPN

Diagnosis

Indications for Testing

• Deep vein thrombosis (DVT), abnormal CBC (most commonly anemia)

Criteria for Diagnosis

• Polycythemia vera (PV)

  2008 WHO diagnostic criteria – both major and 1 minor or the first major criterion and 2 minor must be met Major criteria Evidence of increased RBC volume, including ≥1 of the following Hgb>18.5 g/dL (men), >16.5 g/dL (women) Hgb or Hct >99th percentile of reference Elevated red cell mass >25% above mean predicted Hgb>17 g/dL (men), Hgb>15 g/dL (women) if associated with sustained increase ≥2 g/dL not attributed to correction of iron deficiency anemia Presence of JAK2 (V617F) (90-95%) or JAK2 exon 12 mutations (5-10%) Minor criteria Bone marrow trilineage proliferation Subnormal serum erythropoietin (EPO) level Endogenous erythroid colony growth in vitro

  Essential thrombocythemia (ET)

  WHO criteria 2008 – must meet all 4 criteria Sustained elevation of platelets ≥450x109/L  Defined as at least 2 measurements 2 months apart Bone marrow – megakaryocyte proliferation with little or no granulocyte/erythrocyte proliferation Does not meet WHO criteria for CML, PV, PMF, MDS or other myeloid neoplasm Demonstration of JAK2 (V617F) (50%), MPL gene mutations (eg, W515L and W515K) or no evidence of reactive thrombocytosis Must exclude other causes of thrombocytosis Reactive Anemias Iron deficiency Hemolytic Acute blood loss Post splenectomy Inflammatory disorders Bone marrow biopsy Normal to hypercellular with increased megakaryocytes Stainable iron Normal red cell blood mass No significant collagen or reticulin fibrosis

  Primary myelofibrosis (PMF)

  WHO 2008 criteria – must meet 3 major and 2 minor criteria Major criteria Megakaryocyte proliferation and atypia accompanied by reticulin or collagen fibrosis or, in the absence of reticulin fibrosis, megakaryocyte changes must be accompanied by increased marrow cellularity Does not meet WHO criteria for CML, PV, MDS or other myeloid neoplasm JAK2 (V617F) or similar mutation or no evidence of reactive fibrosis Minor criteria Leukoerythroblastosis Increased serum LD Anemia Splenomegaly

Laboratory Testing

• Initial testing – CBC with differential, EPO level, uric acid, lactate dehydrogenase (LD)
• Rule out most common causes of anemia
  • Nutritional – vitamin deficiency (B₁₂, folate, iron)
  • Gastrointestinal blood loss – fecal blood testing
  • Thyroid disease – TSH
  • Chronic disease – BUN, creatinine, liver function
• Follow with JAK2 (V617F) qualitative, JAK2 (V617F) quantitative, or MPL mutation testing
  • Presence of JAK2 mutation virtually rules out reactive polycythemia
    • If JAK2 (V617F) testing negative, JAK2 exon 12 mutation testing indicated
    • If no JAK2 mutations are found and PV is still considered, perform p50 and VHL mutation gene testing
  • MPL mutation
    • MPL mutation can be used in diagnosis of MPN and suggests either PMF or ET
    • Majority of patients with MPL mutations test negative for JAK2 (V617F) mutation but possess a phenotype consistent with MPN

Histology

• Bone marrow examination
  • Molecular testing for MPN associated with eosinophilia
    • Myeloid neoplasms associated with eosinophilia and abnormalities in PDGFRα, PDGFRβ, or FGFR1
    • Cytogenetic and fluorescence in situ hybridization analysis for detection of FIP1L1-PDGFRα fusion, PDGFRβ (5q33) translocations, or FGFR1 (8p11) translocations
    • In the absence of these molecular markers, CEL-NOS or hypereosinophilic syndrome (HES) is considered
    • Diagnosis in both CEL-NOS and HES requires the following
      • Presence of ≥1.5x10⁹/L eosinophil count (peripheral blood)
      • Exclusion of secondary eosinophilia
      • Exclusion of other acute or chronic myeloid neoplasm
      • No evidence for phenotypically abnormal or clonal T lymphocytes
    • Diagnosis of HES requires the absence of both cytogenetic abnormality and ≥2% peripheral blasts or ≥5% bone marrow blasts
  • Mast cell myeloproliferative neoplasms – CD117 (c-Kit), CD25 testing
• Further testing based on presumed diagnosis

Prognosis

• JAK2 (V617F) – quantitative testing may predict degree of fibrosis, thrombotic tendencies, or survival
• Karyotyping in PMF
  • Unfavorable – complex karyotype or single or two abnormalities, including +8, -7/7q-, i(17q), -5/5q-, 12p-, inv(3), or 11q23

Differential Diagnosis

• Thrombocytosis
  • Primary pulmonary fibrosis and hypertension
  • Malignancy
  • Infection
  • Leukemia
    • Hairy cell leukemia
    • CML
    • CMML
  • Connective tissue diseases
  • Drugs – corticosteroids, adrenaline
  • Hemolysis
  • Hyposplenism
• Anemia
  • Vitamin deficiency – B₁₂, iron, folate
  • Chronic disease – renal, liver
  • Thyroid disease
  • Gastrointestinal bleeding – peptic ulcer disease, malignancy
• Thrombocytopenia
  •  Myelodysplastic syndrome
  • Immune mediated
  • Connective tissue disease
  • Vasculitis
  • Leukemia – AML, ALL
• Thromboses
  • Hereditary thrombophilias
  • Antiphospholipid syndrome
  • Malignancy

Clinical Background

Myeloproliferative neoplasms (MPN) are a group of slow-growing blood cancers, including chronic myelogenous leukemia (CML). MPNs present with clonal proliferation of abnormal hematopoietic cells that involve bone marrow and peripheral blood.

Classification

Selected MPNs

• Polycythemia vera (PV)

  Epidemiology Erythroid dominant trilineage proliferation of hematopoietic precursor cells Incidence – 2.8/100,000 Age – peaks in 50s-60s Sex – M>F (minimal) Clinical Presentation Insidious onset Thrombotic complications Deep vein thrombosis (DVT)  Stroke Myocardial infarction Budd-Chiari syndrome Mesenteric ischemia Transient ischemic attacks Bleeding complications – often associated with acquired von Willebrand disease (vWD) Epistaxis Oral mucosal hemorrhage Gastrointestinal hemorrhage Ecchymoses Hyperviscosity syndrome – less common Hypertension Headache Dizziness Visual disturbances Claudication Erythromelalgia Redness and burning of palms and plantar areas of feet, sometimes progressing to necrosis of digits Gouty arthritis Pruritus Hepatosplenomegaly Transformation to myelofibrosis (or spent phase) – short survival Transformation to acute leukemia – always fatal without allogeneic bone marrow transplant Treatment Many patients asymptomatic and do not require therapy Hydroxyurea Interferon alpha Phlebotomies – controversial Anagrelide Radioactive phosphorus JAK2 tyrosine kinase inhibitors – experimental Allogeneic bone marrow transplant (preferred non-myeloablative) in selected instances

  Essential thrombocythemia (ET)

  Epidemiology Thrombocytosis and abnormal megakaryocyte proliferation with clonal proliferation of pluripotent stem cells Incidence – 1.5/100,000 Age – peaks in 50s  Secondary peak in 20s – mainly females Sex – M:F, equal  Secondary peak – M<F, 1:2 Clinical Presentation Arterial thrombosis Brain Cardiac Extremities Venous thrombosis Lower extremity DVT Portal and hepatic vein thrombosis Pulmonary emboli Bleeding complications Epistaxis Oral mucosal hemorrhage Gastrointestinal hemorrhage Ecchymoses Acquired vWD Many patients are asymptomatic and do not require therapy Transformation to myelofibrosis (or spent phase) in <10% of cases – short survival Transformation to acute leukemia in <5% of cases – always fatal without allogeneic bone marrow transplantation Treatment  Observation Hydroxyurea Interferon alpha – pegylated form much better tolerated Anagrelide Radioactive phosphorus JAK2 tyrosine kinase inhibitors – experimental Allogeneic marrow transplantation (preferred non-myeloablative) in selected instances

  Primary myelofibrosis (PMF)

  Epidemiology Clonal stem cell deficit characterized by panmyelosis with intact maturation, progressive bone marrow fibrosis, splenomegaly, multiorgan extramedullary hematopoiesis Incidence – 0.3-1.5/100,000 per year Age – mean is 67 years Sex – M:F, equal Clinical Presentation May be a secondary process in PV and ET Shortest survival of all MPNs Some with insidious onset and stable; others rapidly progressing Acute leukemic transformation common Symptoms, physical and laboratory findings Hypercatabolic state – fever, weight loss, night sweats High output cardiac failure from increased plasma volume Blood abnormality – dacryocytes (tear drops), leukoerythroblastic morphology Other blood abnormalities – anemia, leukocytosis, leukopenia, thrombocytosis, thrombocytopenia, increased circulating blasts Fatigue unrelated to anemia Dyspnea secondary to anemia Petechia secondary to thrombocytopenia Gout Splenomegaly – 100% of patients Hepatomegaly – 50% of patients Treatment Observation Blood transfusions Androgens Erythropoietin Histone deacetylase inhibitors Splenectomy Hydroxyurea JAK2 tyrosine kinase inhibitors – promising in phase II studies Allogeneic bone marrow transplant (preferred non-myeloablative) in selected instances

Pediatrics

Myeloproliferative neoplasms are extremely rare in children.

Polycythemia vera (PV)

Epidemiology

• Incidence – rare
• Age
  • <0.1% with PV are <20 years
  • Two peaks – 5-6 years, 10-14 years

Clinical Presentation

• Thromboses
  • Arterial – stroke
  • Venous – Budd-Chiari syndrome
• Bleeding disorders
• Splenomegaly common
• Rubor
• Pruritus, especially after hot bath
• Erythromelalgia

Diagnosis

Indications for Testing

• Abnormal CBC

Criteria for Diagnosis

• See Diagnosis tab for PV criteria

Laboratory Testing

• Initial diagnosis – CBC with differential, uric acid, lactate dehydrogenase (LD)
  • JAK2 (V617F) testing, if suspicion for MPN high
  • Bone marrow examination

Indications for Laboratory Testing

• Tests generally appear in the order most useful for common clinical situations
• Click on number for test-specific information in the ARUP Laboratory Test Directory

Click the plus sign to expand the table of additional tests.

Test Name and Number	Comments
CBC with Platelet Count and Automated Differential 0040003 Method: Automated Cell Count/Differential	Initial screen for MPN
Erythropoietin 0050227 Method: Quantitative Chemiluminescent Immunoassay	Initial test for MPN Use to identify or exclude PV (polycythemia vera) – minor criteria
Uric Acid, Serum or Plasma 0020026 Method: Quantitative Spectrophotometry	Initial test for MPN
Lactate Dehydrogenase, Serum or Plasma 0020006 Method: Quantitative Enzymatic	Initial test for MPN
Thyroid Stimulating Hormone with reflex to Free Thyroxine 2006108 Method: Quantitative Electrochemiluminescent Immunoassay
Vitamin B12 & Folate 0070160 Method: Quantitative Chemiluminescent Immunoassay	Rule out alternate cause of anemia
Thyroid Stimulating Hormone 0070145 Method: Quantitative Electrochemiluminescent Immunoassay	Rule out alternate cause of anemia
Urea Nitrogen, Serum or Plasma 0020023 Method: Quantitative Spectrophotometry	Rule out alternate cause of anemia
Creatinine, Serum or Plasma 0020025 Method: Quantitative Enzymatic	Rule out alternate cause of anemia
Hepatic Function Panel 0020416 Method: Quantitative Enzymatic/Quantitative Spectrophotometry	Rule out alternate cause of anemia