Hybrid Molecular Imaging of ER in Breast Cancer Patients With DCIS

Inclusion Criteria: * Diagnosis of biopsy-proven DCIS without invasion or microinvasion measuring at least 1.0 cm in diameter by any imaging modality * Undergoing diagnostic breast MRI ordered by the referring clinician for staging and extent of disease Exclusion Criteria: * Inability or unwillingness to provide informed consent to the study * Surgery, radiation, neoadjuvant chemo/endocrine therapy for the current malignancy prior to study enrollment * Participants currently taking or have taken an ER-blocking medication (e.g. tamoxifen, raloxifene) within 6 weeks prior to study enrollment * Pregnant or lactating women * Participant with intolerance or contraindications for MRI or gadolinium-based contrast agents * Participant girth exceeds the bore of the MRI/PET scanner * Participants with a history of allergic reaction attributable to compounds of similar chemical or biologic composition to 18F-FES * Participants in liver failure as judged by the patient's physician, due to the hepatobiliary clearance of 18F-FES * Participants requiring intravenous (IV) conscious sedation for imaging are not eligible; participants requiring mild, oral anxiolytics for the clinical MRI will be allowed to participate as long as the following criteria are met: * The participant has their own prescription for the medication * The informed consent process is conducted prior to the self-administration of this medication * They come to the research visit with a driver or an alternative p…