The purpose of this study is to measure the safety of the investigational imaging agent, 18F-Var3 and to determine if it is helpful in providing information about how tumor tissues behave.

Inclusion Criteria:

• Age 18 years or greater
• Biopsy-proven breast malignancy
• >/= 1 viable lesion, >/= 1 cm, confirmed on CT, MR, or FDG PET/CT within 4 weeks of protocol enrollment
• Newly diagnosed or recurrent disease, on or off therapy
• ECOG performance of 0-2 *Note: Lesions are considered viable if they are stable or increasing soft tissue lesions, or if they are FDG-avid bone lesions

Exclusion Criteria:

• Life expectancy < 3 months
• Pregnancy or lactation
• Biopsy or other surgical procedures within 48 hours prior to receiving study intervention
• Patients who cannot undergo PT/CT scanning because of weight limits. PET/CT scanners may not be able to function with patients over 400 pounds

Memorial Sloan Kettering Cancer Center supports the international committee of medical journal editors (ICMJE) and the ethical obligation of responsible sharing of data from clinical trials. The protocol summary, a statistical summary, and informed consent form will be made available on clinicaltrials.gov when required as a condition of Federal awards, other agreements supporting the research and/or as otherwise required. Requests for deidentified individual participant data can be made beginning 12 months after publication and for up to 36 months post publication. Deidentified individual participant data reported in the manuscript will be shared under the terms of a Data Use Agreement and may only be used for approved proposals. Requests may be made to: crdatashare@mskcc.org.