Estrogen plays critical roles in regulating the progression of several cancer types, including breast cancer, and the fate of cancer stem cells.[8,9] In this context, ER-positive cancers are responsive to endocrine therapies and sensitive to CDK4/6 inhibitors,[10,11] which suggests that ER positivity may be associated with a better prognosis. The gene discussed is ESR1; the disease is breast carcinoma.