This study will investigate the sensitivity and specificity of FLT-PET/CT in primary breast cancer detection and in the use of FLT-PET in monitoring how well a breast tumor respond to treatment. We will compare this technique with other imaging modalities as well as with tissue collection (during a biopsy). We will recruit women with a newly diagnosed invasive breast cancer, who are able to tolerate undergoing a PET/CT (possibly two scans) scan,

Our overall goal is to use this clinical trial as a platform to validate fibroblast activation protein (FAP) as a biomarker for the tumor microenvironment and to explore the dynamic interaction between proliferating tumor cells and the tumor microenvironment. Our long term goal is to develop new drugs that will target the tumor microenvironment as novel therapeutic and chemoprevention strategies.

Inclusion Criteria:

• Breast biopsy positive for an invasive malignancy (core needle, mammatone, or incisional biopsy)
• Participants must be planning to have surgery at the Hospital of the University of Pennsylvania
• Participants must be able to tolerating lying on the table for about an hour
• Newly diagnosed primary breast cancer, which is classified as being operable (T1-T4)

Exclusion Criteria:

• Pregnant women
• History of severe renal disease
• Prior history of breast cancer of the study breast within the last five years.