Goal of the observational study: Based on PET/MRI data it is possible to differentiate between complete and incomplete pathological remission after neoadjuvant systemic therapy in HER2-positive breast cancer patients. The main question it aims to answer are: Primary endpoint: 1\) Sensitivity and specificity as co-primary endpoints for identification of HER2-positive breast carcinoma with complete pathologic remission (pCR; yT0 yN0) using 18F-FDG PET/MRI (response assessment) Secondary endpoint(s): 1. Accuracy for the identification of patients with HER2-positive breast carcinoma with complete pathologic remission (pCR; yT0 yN0) using 18F-FDG PET/MRI (response assessment) 2. Sensitivity, specificity, and accuracy for the identification of patients with HER2-positive breast carcinoma with complete pathologic remission (pCR) of the primary (yT0) after neoadjuvant therapy using 18F-FDG PET/MRI (response assessment) 3. Sensitivity, specificity, and accuracy for the identification of patients with HER2-positive breast carcinoma with complete pathologic remission (pCR) of locoregional lymph node metastases (yN0) after neoadjuvant therapy using 18F-FDG PET/MRI (response assessment) 4. Evaluation of pre-treatment (baseline) 18F-FDG PET/MRI for predicting therapy response of the primary and locoregional lymph node metastases in patients with HER2-positive breast carcinoma supported by artificial-intelligence (prediction) 5. Evaluation of 18F-FDG PET/MRI for predicting therapy response of the primary in patients with HER2-positive breast carcinoma after the first cycles of systemic therapy supported by artificial-intelligence (prediction) 6. Evaluation of 18F-FDG PET/MRI for predicting therapy response of locoregional lymph node metastases in patients with HER2-positive breast carcinoma after the first cycles of system therapy supported by artificial-intelligence (prediction) The guideline-recommended staging procedure (S3 Germany) using CT will be replaced by a whole-body 18F-FDG PET/MRI, including dedicated 18F-FDG PET/MRI of the breast. The histopathologic results of tissue samples obtained during routine clinical treatment after successful neoadjuvant systemic therapy will serve as a reference standard. The study protocol involves the following examinations for all included patients: 1. Baseline (pre-treatment) examination to substitute for the staging examinations specified in the S3 guideline: Initial whole-body 18F-FDG PET/MRI including 18F-FDG PET/MRI of the breast 2. Thoracic 18F-FDG PET/MRI including 18F-FDG PET/MRI of the breast after the first two cycles of systemic therapy 3. Thoracic 18F-FDG PET/MRI including 18F-FDG PET/MRI of the breast after completion of systemic therapy and immediately before clinically indicated surgery