BRCA2 and breast cancer: Among the common risk factors for breast cancer, such as breast cancer gene 1 (BRCA1) and BRCA2 gene mutations [5], older age [6], family history [7], dense breast tissue [8], and so on, an early onset of menarche, or puberty, is considered to be associated with a higher risk of breast cancer due to the increased number of ovulatory cycles over a lifetime, which results in greater exposure to ovarian hormones and thus a higher risk of breast cancer [9, 10].