Topical Endoxifen in Women

Inclusion Criteria: * Participant in the Karma Cohort * Attending the national mammography screening program, i.e., aged 40-74 and have performed a screening mammogram maximum 3 months prior to study inclusion * Mammographic density \~4.5 % density (volumetric) measured by Volpara, at the screening mammogram performed in connection to baseline (maximum 3 months prior to inclusion). The threshold value of 4.5% corresponds to the clinical Bl-RADS score A * Postmenopausal, defined as no period of menstruation during last 12 months independent of any hormonal treatment * Informed consent must be signed before any study specific assessments are performed Exclusion Criteria: * Any previous or current diagnosis of breast cancer (including carcinoma in situ). * Any previous diagnosis of cancer with the exception of non-melanoma skin cancer and in situ cancer of the cervix. * A history of major surgery of the breast, e.g., reduction or enlargement, which might affect density measurements. * Mammographic Bl-RADS malignancy code 3, or above, at baseline mammography, or at mammography during time of treatment. Recall for additional examinations due to technical problems with the mammogram is accepted. * Currently using estrogen and progesterone based hormone replacement therapy (oral or patches). Local estrogen treatment is accepted (ex. Vagifem). * Non-medical approved drugs against hot-flashes including phytoestrogen.