Rhabdomyosarcoma rarely metastasizes to breast. A 15-year-old adolescent girl underwent FDG PET/CT scan for staging a newly diagnosed alveolar rhabdomyosarcoma. The images showed not only the abnormal activity in the region of the right maxillary sinus, consistent with the known primary tumor, but also an intense focal activity in the right breast. The right breast lesion was excised, and the pathological results showed alveolar rhabdomyosarcoma.