[Participation of fragile sites in cancer].

Structural and numerical chromosomal abnormalities are frequent findings in neoplastic cells. The origin of structural rearrangements is probably due to the existence of specific labile areas on human chromosomes. These areas, named fragile sites (FS), are prone to chromosomal breakage and rearrangements, playing an important role in the first steps of carcinogenesis. The classification of FS, the mechanisms involved in FS induction and their biological significance, specially their relationship with cancer development, are discussed.