Common chromosomal fragile sites exhibit a hierarchy of cytogenetic expression, with FRA3B being more readily observed than FRA16D. DNA instability in cancer cells at FRA3B is also more frequent than that at FRA16D. This finding contributes to a growing body of evidence suggesting that common fragile sites are regions of particular sensitivity to DNA instability and that there is a correlation between the level of in vitro chromosomal fragility and in vivo DNA instability in cancer cells [26,32,33]. Here, FHIT is linked to cancer.