This study is a prospective, non-interventional, open-label study to evaluate the glucose metabolism and the expression of the imaging agent 68 Gallium-Fibroblast Activation Protein Inhibitor-46 (68Ga-FAPi-46) with PET imaging, in woman affected by Breast Cancer (BC) and referred to diagnostic imaging work-up prior to primary therapy.

All patients affected by newly diagnosed, clinically N-positive BC that have already undergone a baseline 2-deoxy-2-[fluorine-18]fluoro-D-glucose (18F-FDG) PET/CT (T1) will be screened for eligibility. Patients who will meet all inclusion/exclusion criteria will be considered eligible and asked to participate to the study after signing the informed consent form. Patients' eligibility will be evaluated by the referent nuclear medicine physician (T2). Considering the clinical experience of the investigators, we expect to complete patient enrolment in 12 months after study accrual

Inclusion Criteria:

• Newly diagnosed, biopsy proven breast cancer;
• Diagnosis of invasive breast cancer;
• Tumor diameter more than 2 centimeters;
• Radiological evidence of axillary nodes involvement;
• 18F-FDG PET/CT performed as baseline diagnostic procedure, during routine diagnostic work-up;
• 68Ga-FAPi-46 PET/CT performed within 4 weeks from 18F-FDG PET/CT;
• Patients suitable to primary treatment (surgery or neo-adjuvant therapy);
• 68Ga-FAPi-46 PET/CT performed within 8 weeks from primary treatment;
• Female patients;
• Age ≥18;
• Willing to sign informed consent form.

Exclusion Criteria:

• Pregnant or nursing patients;
• Unable to stay flat and cannot tolerate PET scan;
• Sample tissue from biopsy unavailable for assessing Fibroblast Activation Protein (FAP) expression;
• Eastern Cooperative Oncology Group (ECOG) performance status ≥2.