chronic lymphocytic leukemia (CLL) is a type of leukemia that is characterized by an increase in B lymphocytes. CLL normally does not produce anomalies or symptoms for a number of years because its development is so slow. Also, some patients never develop symptoms.

Chromosome-level changes are seen in most cases of CLL. The most common changes include loss of chromosomes 11, 13, or 17 (deletion), changes in the genetic material between chromosomes (translocation), and trisomy 12.