Chromosomal abnormalities: Detection and implications for cancer development

The occurrence of chromosomal abnormalities is a common theme in carcinogen esis. A large proportion of tumours which have been characterized at the cy togenetic level carries numerical and/or structural aberrations. Numerical alterations may include acquisition ol loss of specific chromosomes ol dram atic changes in overall ploidy levels. Structural aberrations may include D NA amplifications ol deletions, inversions and translocations. Many chromos omal alterations occur in a non-random fashion and may be subdivided bz to primary and secondary, according to their timing of occurrence. Primary chr omosomal abnormalities usually occur at the early stages of tumourigenesis and are often encountered as sole cytogenetic abnormalities. Secondary chro mosomal abnormalities are usually associated with more advanced stages of t umour development. In recent years several chromosomal abnormalities could be col related with specific gene alterations, thus providing insights into the molecular mechanisms understanding tumourigenesis. The biological cons equences imparted by other chromosomal changes such as numerical changes ar e, however, less cleat: By using recently developed molecular techniques fo r chromosome characterization so-called molecular cytogenetics, ou, percept ion on cancer cytogenetics is rapidly changing through the disclosure of hi therto unknown (specific) chromosomal abnormalities.