Another receptor involve in tumorigenesis and breast cancer development is progesterone receptor (PgR) . This receptor belongs to the nuclear receptor family commonly known as oestrogen receptor (ER)-regulated gene family, expressed in around two-thirds of ERpositive (ERþ) breast cancers patients . The role of progesterone in breast cancer etiology is increasingly clear. It is plausible that during repeated menstrual cycles, frequent activation of progesterone receptor and its downstream effectors including cyclin D1, WNT4 and RANKL stimulate the breast carcinogenesis . The significance of endogenous estrogens and progesterone in the development of breast cancer is also obvious from the strong associations between breast cancer and women's reproductive factors, such as age at menarche, age at menopause, and parity . These established risk factors for breast cancer can be thought as measures of the cumulative 'dose' of estrogen and progesterone to which breast epithelium is exposed over time .