Genetic instability is one of the most characteristic features of cancer cells. It is expressed in the cell accumulation of chromosomal aberrations and mutation, as well as microsatellite instability and loss of heterozygosity. Microsatellite instability (MSI) is a mutator phenotype characteristic. It occurs in hereditary and sporadic cancers, although with different frequencies. MSI is to change the length (size) alleles by increasing or reducing the number of nucleotide repeats.

Genetic instability, chromosomal or / and microsatellite is one of the characteristics of tumor cells. In tumor cells, both solid tumors and hematologic malignancies chromosomal instability expressed by the accumulation of structural and numerical aberrations of chromosomes. Chromosomal aberrations in tumors may be changes in specific, critical for the transition process, or secondary, which are the expression and at the same time cause genetic instability of cancer cells.