Unsuspected metastatic male breast nodule from synovial sarcoma detected by FDG PET

The literature of serendipitous findings on whole-body FDG PET continues to grow. Whole-body FDG PET imaging of a 24-year-old man with treated synovial sarcoma of the right upper extremity showed an abnormal focus of activity over the right chest in addition to abnormal uptake in the lungs. On reexamination, he was found to have a hitherto unknown 2.5-cm mobile nodule in the right breast. Histopathology confirmed it to be metastasis from the synovial sarcoma. Extramammary malignancies metastasizing to the breast constitute approximately 2% of all breast tumors.