Of the rare CNVs associated with malignancy, the gene most frequently associated with BC development is the tumour suppressor FHIT. FHIT has been reported multiple times to be genetically and epigenetically modified in breast tumours [36-41]; its expression has been reported to be protective against HER2-driven breast tumour development [42]; whereas reduced expression is associated with poor prognosis [43]. This evidence concerns the gene ERBB2 and breast cancer.