The progesterone receptor gene (PGR, commonly known as PR) plays a role in pathogenesis of cancers such as endometrial cancer and breast cancer (Kim et al. 2013). PR is located on chromosome 11 (Law et al. 1987). PR is in the nuclear receptor superfamily, is part of the steroid receptor family, and has a six-region structure with a defined functional domain (Grontved and Hager 2012).
PR protein expression is measured using immunohistochemistry (IHC) and PR expression occurs in 55–58% of invasive breast cancers (Nadji et al. 2005; Rhodes et al. 2000) and in 50–72% of endometrial cancers (Merritt et al. 2010; Suthipintawong et al. 2008).