Purpose To investigate the ability of 18F-FDG PET/CT imaging to detect metastases not detected by conventional imaging (CT and bone scintigraphy) in patients diagnosed with stage II/III and locoregional recurrent breast cancer (BC) which can affect the choice of treatment. Hypothesis The hypothesis is that 18F-FDG PET/CT can provide information about disease stage beyond the currently used conventional imaging (CT and bone scintigraphy) in patients diagnosed with stage II/III or locoregional recurrent BC. Objectives Primary: To evaluate if a 18F-FDG PET/CT scan in the initial work up of patients diagnosed with stage II/III or locoregional recurrent BC will lead to change in staging and/or treatment. Secondary: * Overall survival (OS) and progression-free survival (PFS) in the patients with upstaging based on findings on 18F-FDG PET/CT scan compared with the patients with unchanged stage of disease following 18F-FDG PET/CT. * Obtain size of the primary BC from CT/MRI scan and evaluate if these metrics are correlated to outcome. * Obtain PET parameters from the primary BC: maximum, mean, and peak standardized uptake value (SUVmax, SUVmean, SUVpeak), metabolic tumour volume (MTV), total lesion glycolysis (TLG), total MTV and total TLG and evaluate if these metrics are correlated with outcome. * Obtain CT and PET texture parameters from the primary BC and evaluate if these metrics are correlated with outcome. * Blood and tumor samples for molecular characterisation: