We describe a pulmonary metastasis of a cystosarcoma phyllodes of the breast (CPB) detected by F-FDG PET/CT. A 65-year-old female patient previously operated on for a cystosarcoma phyllodes of the left breast underwent F-FDG PET/CT for restaging. F-FDG PET/CT showed an area of increased F-FDG uptake corresponding to a 2-cm right pulmonary nodule. Histology suggested the presence of a pulmonary metastasis of CPB.