Myelodysplastic Syndromes

Key Points

Cytogenomic SNP Microarray in Myelodysplastic Syndrome (MDS)

Genetic studies are required at the time of diagnosis of MDS not only for identifying specific genetic abnormalities but also for monitoring disease progression.  Unfortunately, more than half of patients with MDS have a normal karyotype, making disease-monitoring difficult in these patients. Patients with a normal karyotype but aggressive disease may have abnormalities that cannot be identified by FISH or conventional cytogenetics. Cytogenomic SNP microarray is the test of choice for these patients.  Cytogenomic SNP microarray can detect both copy-number variation (loss or gain of DNA) in addition to loss of heterozygosity (LOH), which is often due to mutations and subsequent selection of mutant tumor-suppressor genes and oncogenes. In addition, cytogenetically-identified abnormalities may be monitored by FISH.

• Conventional cytogenetics, FISH, and cytogenomic SNP microarray comparisons (see table below)

Diagnosis

Indications for Testing

• Abnormal CBC or peripheral smear without other obvious etiology – may see macrocytic anemia, other cytopenias, dysplastic cells in peripheral smear

Criteria for Diagnosis

• International Consensus Working Group recommendations
  • Stable cytopenia for >6 months
    • 2 months if accompanied by specific karyotype or bilineage dysplasia
  • Exclusion of other potential disorders as a primary reason for dysplasia or cytopenia
  • At least one MDS-related decisive criterion
    • Dysplasia (≥10% in ≥1 of the 3 major bone marrow lineages)
    • Blast cell count of 5-19%
    • Specific MDS-associated karyotype [eg, del(5q), del(20q), +8, -7/del(7q)]
  • Co-criteria help confirm the diagnosis
    • Bone marrow histology and immunohistochemistry to detect fibrosis, dysplastic megakaryocytes, atypical localization of immature progenitors
    • Flow cytometric analysis to identify abnormal myeloid antigen patterns, abnormal CD34 expression in blasts
    • Molecular markers to detect myeloid clonality

Histology

• Classification based on bone marrow histology, immunohistochemical features, flow cytometry and cytogenetic FISH findings
  • Bone marrow biopsy – diagnosis almost exclusively made using marrow appearance
    • Criteria – dysplasia in ≥10% of myeloid lineage cells
  • Cytogenetic testing for recurrent chromosome abnormalities consistent with MDS
    • FISH – does not add substantially for cytogenetically normal cases
    • Microarray – identification of MDS-associated imbalances and loss of heterozygosity in ~20% of cases with normal cytogenetic chromosome analysis
    • Most common abnormalities – del(5q) and del(7q), trisomy 8
    • Non-therapy related
      • Good prognosis
        • Isolated del(5q) or del(20q)
      • Poor prognosis
        • Del(7q)
        • ≥3 cytogenetic abnormalities
    • Therapy-related
      • Good prognosis
        • Del(5q) – only if sole abnormality
      • Poor prognosis
        • Monosomy 7 – 50% of cases
        • Del(7q) – 5-10% of cases
        • 11q23 rearrangements with MLL – associated with anti-topomerase II treatment
    • See Key Points tab for comparison of FISH conventional cytogenetics and cytogenetics SNP microarray in diagnosis of MDS
• Other modalities in difficult to diagnose cases
  • Flow cytometry
    • Changes not specific for MDS; may be most useful in ruling out other neoplasms in patient with cytopenias
      • Absence of  flow cytometric abnormalities does not exclude MDS
  • Immunohistochemistry – CD117 (c-Kit); CD34 (QBEnd/10); myeloperoxidase (MPO) to identify abnormal localization of immature precursors and increased blasts

Prognosis

• Most accurately defined by cytogenetic testing, FISH & cytogenetic SNP microarray
• Dependent on karyotype, % blasts, and number of cytopenias present
• MDS International Prognostic Scoring System (IPSS)

  Combines information on bone marrow blast percentage, cytogenetic abnormalities and type(s) of cytopenia into low-, intermediate-, and high-risk disease Low risk – normal karyotype, isolated del(5q), isolated del(20q), -Y, <5% cell blasts, 0-1 cytopenias (IPSS score = 0) Median survival – 15.7 years 25% will progress to AML in ~9 years High risk – abnormalities of chromosome 7 or complex karyotype with three or more abnormalities; >10% cell blasts and two or more cytopenias (IPSS score ≥2.5) Median survival – 0.4 years 25% will progress to AML within 2-3 months Intermediate risk – all other abnormalities Median survival – 3.5 years 25% will progress to AML in ~3 years

• Newest prognostication from WHO classification-based scoring system incorporates transfusion burden
  • Poor prognosis with refractory anemia with excess blasts (RAEB) or refractory anemia with excess blasts in transformation (RAEB-t)
    • Median survival 5-12 months
    • Disease transforms to AML in 40-50%
  • Better prognosis with refractory anemia (RA) or refractory anemia with ring sideroblasts (RARS)
    • Median survival 3-6 years
    • Disease transforms to AML in 5-15%

Differential Diagnosis

• Cytopenias
  • Pancytopenia
    • Medication/toxin exposure
    • Bone marrow failure – aplastic anemia
    • Hemophagocytic syndrome
    • Acute leukemias – AML, ALL
    • Alcohol abuse
    • Infections
    • Severe nutritional deficiency
• Isolated anemia
  • Parvovirus
  • HIV
  • Toxins
  • Blood loss or hemolysis
  • Vitamin deficiencies – B₁₂, folate
• Isolated neutropenia
  • Acute leukemias (AML, ALL)
  • Medications – sulfonamides, ganciclovir
  • HIV
  • Hypersplenism
  • Familial cyclic neutropenia
  • Antineutrophil antibodies associated with autoimmunity or tumors
• Isolated thrombocytopenia
  • Idiopathic thrombocytopenic purpura
  • Hypersplenism
• Dyserythropoiesis
  • Ring sideroblasts
    • Toxins – arsenic, zinc, lead
    • Deficiencies – copper, pyridoxine
    • Medications – tuberculosis treatment
  • Congenital dyserythropoiesis
• Other
  • Paroxysmal nocturnal hemoglobinuria
  • Myeloproliferative/myelodysplastic neoplasms

Clinical Background

Myelodysplastic syndromes (MDS) are clonal hematopoietic malignancies characterized by ineffective hematopoiesis, cytopenia, unilineage or multilineage dysplasia and a susceptibility to leukemia, especially AML.

Epidemiology

• Incidence  
  • 5/100,000 in the general population
  • 22-45/100,000 in the elderly population (>70 years)
• Age – median is 65-70
• Sex – M>F

Classification

• World Health Organization (WHO) classification of MDS

  MDS Subtype	2008 WHO Classification
  	Blood	Bone Marrow
  Refractory cytopenias with unilineage dysplasia (RCUD)	Unicytopenia or bicytopenia1 No or rare blasts (<1%)2	Unilineage dysplasia ≥10 % of one cell line <5% blasts <15% of erythroid precursors are ring sideroblasts
  Refractory anemia (RA)
  Refractory neutropenia (RN)
  Refractory thrombocytopenia (RT)
  Refractory anemia with ring sideroblasts (RARS)	Anemia No blasts	≥15% erythroid precursors are ring sideroblasts Erythroid dysplasia only  <5% blasts
  Refractory cytopenia with multilineage dysplasia (RCMD)	Cytopenia(s) No or rare blasts (<1%) No Auer rods <1x109/L monocytes	Dysplasia in ≥10% of cells in ≥2 myeloid lineages  ±15% ring sideroblasts <5% blasts No Auer rods
  Refractory anemia with excess blasts-1 (RAEB-1)	Cytopenia(s) <5% blasts No Auer rods <1x109/L monocytes	Unilineage or multilineage dysplasia No Auer rods 5-9% blasts
  Refractory anemia with excess blasts-2 (RAEB-2)	Cytopenia(s) 5-19% blasts Auer rods <1x109/L monocytes	Unilineage or multilineage dysplasia Auer rods ± 10-19% blasts
  Refractory anemia with excess blasts in transformation (RAEB-t)	subtype not used
  Myelodysplastic syndrome, unclassified (MDS-U)	Cytopenias ≤1% blasts	Unequivocal dysplasia in <10% of cells in ≥1 myeloid cell lines when accompanied by a cytogenetic abnormality considered as presumptive evidence for a diagnosis of MDS  <5% blasts
  MDS associated with isolated del(5q)	Anemia Platelets normal or increased No or rare blasts (<1%)	Normal to increased megakaryocytes with hypolobated nuclei Isolated del(5q) <5% blasts No Auer rods
  Chronic myelomonocytic leukemia (>1,000 monocytes/µL blood)	subtype not used
  1Bicytopenia may occasionally be observed; cases with pancytopenia = MDS-U 2If marrow myeloblasts <5% but 2-4% myeloblasts in blood = RAEB-1 3Auer rods and <5% myeloblasts in blood and <10% in marrow = RAEB-2 Note: NCCN endorses using both the French-American-British (FAB) and WHO classification criteria for RAEB-t patients

Risk Factors

• Increased age
• Occupational exposures
  • Benzene-containing products
  • Pesticides
  • Organic solvents
  • Heavy metals (lead, arsenic)
• Drug exposures
  • Alkylating agents, other cytotoxic agents
  • Azathioprine
  • Mycophenolate
• Therapy-related – 10-15% of MDS occurs following chemotherapy and radiation treatment
• Genetic
  • Fanconi anemia
  • Familial myelodysplasia
  • Diamond-Blackfan syndrome

Pathophysiology

• Clonal expansion of the multipotential hematopoietic cell
• Primary mechanism is defective maturation of marrow cells coupled with premature cell death

Clinical Presentation

• May be asymptomatic
  • Disease is generally indolent, with blood counts remaining relatively stable over several months or longer
• Most common symptoms
  • Anemia – pallor, weakness, exertional dyspnea
  • Increased infection from neutropenia
  • Bleeding/bruising from thrombocytopenia
• Complications
  • 25-30% progress to AML; incidence depends on MDS subtype
    • Lower response rate to standard therapy for patients >65 years with de novo AML
  • Death from complications of cytopenia (neutropenia in particular)

Pediatrics

Clinical Background

Epidemiology

• Incidence – 0.5-4/1,000,000 (rare)
• Age – 6-8 years

Classification

• Patients with 2-19% blasts in peripheral blood and/or 5-19% blasts in bone marrow may be classified using the adult schema provisional but excludes patients with Down syndrome
• Additional pediatric entity of refractory cytopenia of childhood is recognized
  • <2% blasts in peripheral blood and <5% blasts in bone marrow
  • Bilineage dysplasia

Clinical Presentation

• May be asymptomatic
• Most common symptoms
  • Anemia – pallor, weakness, exertional dyspnea
  • Hepatomegaly/splenomegaly (5-10%)
  • Arthralgias

Diagnosis

• Refer to Diagnosis and Key Points tabs

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
Chromosome Analysis, Bone Marrow 2002292 Method: Giemsa Band	Identify recurrent chromosome abnormalities consistent with MDS
Chromosome Analysis, Leukemic Blood 2002290 Method: Giemsa Band	Identify recurrent chromosome abnormalities consistent with MDS
Leukemia/Lymphoma Phenotyping by Flow Cytometry 2008003 Method: Flow Cytometry	Initial test when evaluating hematopoietic neoplasms (ie, leukemia, lymphoma) Monitor therapy in patients with established diagnosis of hematopoietic neoplasms Specimens include peripheral blood, bone marrow, and tissue Markers selected based on clinical history, previous flow studies, and pathologist interpretation Available markers Myelo/Mono: CD11b, CD13, CD14 (Mo2), CD14 (MY4), CD15, CD33, CD64, CD117, myeloperoxidase T cell: CD1, CD2, CD3, CD4, CD5, CD7, CD8, TCR alpha-beta, TCR gamma-delta, cytoplasmic CD3 B cell: CD10, CD19, CD20, CD22, CD23, CD103, kappa, lambda, FMC7, cytoplasmic kappa, cytoplasmic lambda Misc: CD11c, CD16, CD25, CD30, CD34, CD38, CD41, CD42b, CD45, CD56, CD57, CD61, HLA-DR, glycophorin, TdT, bcl-2, ALK-1, CD123, CD138, CD200, CD26, CD45