Clinical and biological importance of cytogenetic abnormalities in childhood and adult acute lymphoblastic leukemia.

Among the approximately 7,000 cytogenetically abnormal childhood and adult B- and T-lineage acute lymphoblastic leukemias (ALL) published to date, numerous recurring chromosomal aberrations and abnormality patterns have been identified, and it has been clearly shown that the cytogenetic features often correlate closely with specific morphologic, immunophenotypic, and clinical parameters. Thus, karyotypic investigations are now routinely performed for diagnostic and prognostic purposes in ALL, with the chromosomal abnormalities/cytogenetic patterns playing a major role for proper risk assessment and choice of treatment. At the same time, the cytogenetic analyses have resulted in the identification of more than 70 different genes, located at the breakpoints of ALL-associated structural chromosomal abnormalities, that are causally implicated in the leukemogenic process. Hence, the genetic studies have also improved our understanding of the mechanisms of leukemogenesis. However, the almost staggering amount of cytogenetic information presently available has made it increasingly difficult to obtain a general overview of the clinical and biological importance of karyotypic patterns in ALL. Here, we summarize and review the cytogenetic features of childhood and adult ALL, with emphasis on their molecular genetic consequences and their clinical impact.