**2. Epidemiology**

MDS's incidence increase markedly with age, and the classical patient will be in their late 60s or 70s and have one or more otherwise unexplained cytopenia [4, 5].

The incidence is 4 to 5 per 100,000 persons per year, the direct etiology for MDS is usually unknown. However, in 15 to 20% of cases, MDS are secondary (sMDS) to chemotherapy and/or radiotherapy for an other disease. Some times, MDS can be, secondary to exposure to benzene or other aromatic hydrocarbons, or products used in agriculture.

The pathophysiology of MDS and its progression to AML involve cytogenetic, genetic, and epigenetic factors [6].

Now, it is well recognized that MDS is, like other cancers, shaped by recursive rounds of positive selections, where gene mutations and other genetic alterations play central roles.

#### **3. WHO Classification of MDS**

The classification of Tumours of Haematopoetic and Lymphoid Tissues done by the World Health Organization (WHO) defines MDS as a clonal, stem cell disorder.

The 2016 new revision of this classification defines ten MDS subtypes. The first subtype is defined by MDS with single lineage dysplasia (MDS-SLD), the second one is characterized by MDS with dysplasia in two or more myeloid lineages (MDS-MLD). Third subtype is MDS-SLD/MLD with ≥15% ring sideroblasts (RSs; MDS-MLD-RS). An excess of blasts of up to 9% in bone marrow and up to 4% in peripheral blood define MDSEB- 1, and MDS with 10–19% bone marrow and 5–19% blood blasts define MDS-EB-2. An other subtype is present on this classification, it s MDS with isolated deletion of chromosome 5q [del(5q)]. Finally, we found MDS unclassifiable (MDS-U) based on defining cytogenetic abnormality, MDS-U with SLD and pancytopenia and MDS-U with 1% blood blasts [7].

**Table 1** summarizes 2016 OMS classification of MDS.

#### **4. Evolution/prognostic**

Until 2016, del(5q) was the only genetic marker implicated in MDS classification. In the updated classification, identification of SF3B1 mutation determines MDS-RS (even when the RS count is >5–15%).

The revised International Prognostic Scoring System (IPSS-R) for MDS propose 5 risk groups depending on number and severity of cytopenia. Its include also the percentage of bone marrow blasts and cytogenetic aberrations **Figure 1** [7].

Cytogenetic abnormalities were categorized into 5 prognostic subgroups that were shown to have significant prognostic relevance with different median survival and risk of evolution into AML.

The molecular profile of MDS has become a vital factor in assessing the risk of patients with MDS and making treatment decisions. Health care providers must understand when to order genetic testing, how to interpret the results, and the

**117**

**Name** MDS with single lineage dysplasia (MDS-SLD)

MDS with multilineage dysplasia (MDS-MLD)

**MDS with ring sideroblasts (MDS-RS)**

MDS-RS with single lineage dysplasia (MDS-RS-SLD)

MDS-RS with multllineage dysplasia (MDS-RS-MLD)

MDS with Isolated del(5q)

**MDS with excess blasts (MDS-EB)**

MDS-EB-1 MDS-EB-2

0–3 0–3

1–3

None or any

BM 10–19%

Any

or PB 5–19%

or Auer rods

1–3

None or any

BM 5–9% or

Any

PB 2–4%, no

Auer rods

2 or 3

1–3

1–2

None or any

BM <5%, PB

del(5q) alone or with 1 additional abnormality except

−7 or del (7q)

<1%, no Auer

rods

1–3

≥15%/≥5%†

BM <5%, PB

Any, unless fulfills all criteria for MDS with isolated

del(5q)

<1%, no Auer

rods

1

1 or2

≥15%/≥5%†

BM <5%, PB <1%, no Auer rods

Any, unless fulfills all criteria for MDS with isolated del(5q)

2 or 3

1–3

<15%/<5%†

BM <5%, PB <1%, no Auer rods

Any, unless fulfills all criteria for MDS with isolated del(5q)

1

1 or2

<15%/<5%†

BM <5%, PB <1%, no Auer rods

Any, unless fulfills all criteria for MDS with isolated del(5q)

**Dysplastic lineages**

**Cytopenias\***

**Ring sideroblasts as % of marrow erythroid elements**

**BM and PB blasts**

**Cytogenetics by conventional karyotype analysis**

*Cytogenetic and Genetic Advances in Myelodysplasia Syndromes*

*DOI: http://dx.doi.org/10.5772/intechopen.97112*


#### *Cytogenetic and Genetic Advances in Myelodysplasia Syndromes DOI: http://dx.doi.org/10.5772/intechopen.97112*

*Cytogenetics - Classical and Molecular Strategies for Analysing Heredity Material*

deregulation participate to this differentiation defect [3].

and genetics of MDS and related disorders.

genetic, and epigenetic factors [6].

**3. WHO Classification of MDS**

**4. Evolution/prognostic**

and risk of evolution into AML.

MDS-RS (even when the RS count is >5–15%).

**2. Epidemiology**

in agriculture.

play central roles.

accumulation and peripheral cytopenias. Microenvironmental changes and immune

The purpose of this review is to overview the recent advances in the cytogenetics

MDS's incidence increase markedly with age, and the classical patient will be in their late 60s or 70s and have one or more otherwise unexplained cytopenia [4, 5]. The incidence is 4 to 5 per 100,000 persons per year, the direct etiology for MDS is usually unknown. However, in 15 to 20% of cases, MDS are secondary (sMDS) to chemotherapy and/or radiotherapy for an other disease. Some times, MDS can be, secondary to exposure to benzene or other aromatic hydrocarbons, or products used

The pathophysiology of MDS and its progression to AML involve cytogenetic,

Now, it is well recognized that MDS is, like other cancers, shaped by recursive rounds of positive selections, where gene mutations and other genetic alterations

The classification of Tumours of Haematopoetic and Lymphoid Tissues done by the World Health Organization (WHO) defines MDS as a clonal, stem cell disorder. The 2016 new revision of this classification defines ten MDS subtypes. The first subtype is defined by MDS with single lineage dysplasia (MDS-SLD), the second one is characterized by MDS with dysplasia in two or more myeloid lineages (MDS-MLD). Third subtype is MDS-SLD/MLD with ≥15% ring sideroblasts (RSs; MDS-MLD-RS). An excess of blasts of up to 9% in bone marrow and up to 4% in peripheral blood define MDSEB- 1, and MDS with 10–19% bone marrow and 5–19% blood blasts define MDS-EB-2. An other subtype is present on this classification, it s MDS with isolated deletion of chromosome 5q [del(5q)]. Finally, we found MDS unclassifiable (MDS-U) based on defining cytogenetic abnormality, MDS-U

Until 2016, del(5q) was the only genetic marker implicated in MDS classification. In the updated classification, identification of SF3B1 mutation determines

The revised International Prognostic Scoring System (IPSS-R) for MDS propose 5 risk groups depending on number and severity of cytopenia. Its include also the percentage of bone marrow blasts and cytogenetic aberrations **Figure 1** [7].

Cytogenetic abnormalities were categorized into 5 prognostic subgroups that were shown to have significant prognostic relevance with different median survival

The molecular profile of MDS has become a vital factor in assessing the risk of patients with MDS and making treatment decisions. Health care providers must understand when to order genetic testing, how to interpret the results, and the

with SLD and pancytopenia and MDS-U with 1% blood blasts [7]. **Table 1** summarizes 2016 OMS classification of MDS.

**116**


*‡One percent PB blasts must be recorded on at least 2 separate occasions.*
