CHEK2 and breast cancer: The CHEK2 gene is mainly linked to ovarian cystadenomas, borderline ovarian tumors, and low-grade invasive cancers [42], but at the same time this gene is involved in DNA damage response and is associated with a moderate risk of breast cancer [18] and also a risk of other tumors [43], such as prostate [44,45,46], colorectal [47], and gastric cancers [48].