In our study, in the example of breast cancer, it was shown that the presence of amplified chromosomal regions with localization of stem genes in the tumour is associated with the ability to metastasise, determining the possibility of dedifferentiation of CD44−CD24− cells of primary breast tumour cultures in CD44+CD24− CSCs with active proliferation and mammary formation [150]. This evidence concerns the gene CD44 and breast cancer.