ERs are often significantly overexpressed in many cancers, such as mammary adenocarcinoma, and specifically the lack of expression of the ESR2 gene is closely related to the occurrence and progression of cholangiocarcinoma (Haldosén, Zhao & Dahlman-Wright, 2014; Mahdavipour et al., 2017; Zhang et al., 2018; Carrillo et al., 2019). The gene discussed is ESR2; the disease is cancer.