ERBB2 and breast cancer: While breast cancer commonly metastasizes to other organs (such as the lungs and bones), in addition to the brain, our study focused on the association between 18F-FDG PET uptake and the HER2 status of breast cancer brain metastases because patients with HER2-positive breast cancer have a greater likelihood of developing brain metastases, and determining the HER2 status of breast cancer brain metastases noninvasively has a direct impact on clinical management.