**5.6 Complex karyotypes**

Karyotypes is considered as Complex (15%) by the presence of at least 3 anomalies that are thought to result from alterations in DNA repair or checkpoint signalling. Complex karyotypes are usully heterogeneous. The prognosis of patient having complex karyotype is worsening with each additional aberration, rather than by the chromosomes involved (most frequently, 5, 7 and 17). Complex karyotypes are by essence chemoresistant, but interesting results with the hypomethylating agent decitabine have been described by some studies.
