The abnormal proliferation of white blood cells causes a type of cancer known as leukemia. Leukemia is primarily caused by chromosomal instability, which leads to the transfer of genes from one chromosome to another, with or without fusion or juxtaposition of two different genes. This phenomenon is known as translocation and causes a change in the rate expression of the translocated genes. Translocations can therefore lead either to gene fusions or to the juxtaposition of oncogenes to other genes. At presently, it is known at least ten different types of gene fusion and nine types of juxtapositions associated with leukemia.

Leukemia itself is divided into two different types: lymphocytic leukemias and myelogenous leukemias. Lymphocytic leukemias occur when a given translocation affects lymphoid cells, which induces its overproduction and accumulation in lymphocytic tissues and lymph nodes, with the consequent spread to other areas of the body. When the translocation...