The 18 fluorodeoxyglucose-positron emission tomography (18FDG-PET) scan is a valuable, well established tool for diagnostic staging in numerous cancer sites, as well as for locally advanced BC to detect distant metastasis. Positron-emission tomography (PET) is a non-invasive imaging method that uses positron-emitting isotopes. It has been used increasingly frequently in clinics, especially in oncology. The most commonly used radiopharmaceutical, FDG tagged with fluorine-18 (18F-FDG) is a glucose analog whose FDG involvement in tissues is in proportion to the use of glucose; it is taken up into cells like glucose but cannot be metabolized. According to the National Comprehensive Cancer Network (NCCN) guidelines, PET/CT is not routine for early diagnosis of breast cancer (BC). Although PET/CT is not routinely recommended for establishing the diagnosis of BC, it may disclose important information about some histo-pathological features of the primary tumor. The uptake of FDG was negatively correlated with hormonal receptor status in patients with large or locally advanced invasive ductal carcinoma. Moreover, the functional nature of PET imaging may provide the possibility of texture analysis in assessing tumor heterogeneity as a new tool for assessment of tumor aggressiveness. The diagnostic accuracy of PET/CT for distant metastasis has been evaluated in multiple studies. The results of a meta-analysis suggested that PET/CT is a valuable alternative when conventional MRI shows indeterminate or benign lesions or is not applicable.