**Abstract**

Genetic defects play a major role in pathogenesis of the most of haematological malignancies, including cytogenetic abnormalities, gene mutations, and abnormal gene expression. Our knowledge about the genetics of haematological disorders has been dramatically improved during the past decade, due to revolution of sequencing technologies which have played a crucial role. In this chapter, we describe the techniques commonly employed for elucidating chromosomal aberrations, prognostic impact of recurrent chromosomal abnormalities, and recently updated risk stratification systems. We will summarise the chromosomal abnormalities recently identified on many of haematological diseases such acute myeloid leukaemia, acute lymphoid leukaemia, myelodysplasic syndrome, multiple myeloma, meyloproliferative disease and clarify their impacts on clinical phenotype and prognosis, as well as their role in the pathogenesis of these diseases. The aim of this chapter is to provide a brief overview of the recent progresses in haematological diseases genetics.

**Keywords:** clonal evolution, cytogenetic, somatic mutation, chromosomal abnormality, WHO classification

## **1. Introduction**

The few recent years seen revolution on genetic technic with a big improvement of new technology. Haematological malignancy benefits from this development. Geneticists cooperate closely with hemato-oncologists; this cooperation improves many aspect of hemato-oncologists practice. It s can be helpful for diagnostic tests but also the key its allow also a better knowledge of cancer genetics which helps the specialist assess prognosis of their patient, selection of the most appropriate anticancer therapy, and monitoring the response to treatment [1].

Cytogenetic techniques occupied an important place in haematological diagnostics. The first chromosomal aberration described was in 1960 by Nowel and Hungeford characteristic, it was about CML- Philadelphia chromosome, few years after, it was be proved that almost every haematological neoplasm possess was associated with karyotype abnormalities [2].

ON 1980s, new method was developed: fluorescence in situ hybridization (FISH), it s characterised by high sensitivity and specificity, this technic has an other major particularity, it can be performed rapidly, and can classified the nature of chromosomal abnormalities [3].

Over the last few years, more powerful technologies were developed, the most remarkable one is was the Next-generation sequencing (NGS) witch was a real revolution on haematology [4].

In this chapter, we describe the techniques commonly employed for elucidating chromosomal aberrations, prognostic impact of recurrent chromosomal abnormalities, and recently updated risk stratification systems.

We will summaries the chromosomal abnormalities recently identified on many of haematological diseases such acute myeloid leukaemia, acute lymphoid leukaemia, myelodysplasic syndrome, multiple myeloma, meyloproliferative disease and clarify their impacts on clinical phenotype and prognosis, as well as their role in the pathogenesis of these diseases.

The aim of this chapter is to provide a brief overview of the recent progresses in haematological diseases genetics.
