Purpose of review: This review discusses numerical and structural chromosomal instability in cancer cells and its possible etiologies, highlighting the recent literature.
Recent findings: Defects in chromosomal segregation, telomere stability, and the DNA damage response play significant roles in chromosomal instability in cancer.
Summary: The pace of discoveries into the biologic basis of chromosomal instability in cancer cells is quickening and the various causes, previously thought to be unrelated, are being found to be intertwined. Because chromosomal instability is likely to be a main mechanism behind tumor evasion of therapy, understanding the causes and their implications for diagnostic and prognostic evaluation and therapy is of tantamount importance.