Incidental primary breast cancer detected on PET–CT

The purpose of this study is to determine the incidence of primary breast cancer (PBC) detected on (18) F-fluorodeoxyglucose (FDG) positron emission tomography (PET)–computed tomography (CT) in patients with a known diagnosis of non-mammary malignancies. A database search was performed to identify patients with non-mammary malignancies who had undergone staging with FDG PET–CT at a single institution between September 2005 and September 2011 and with the word “breast” reported in the PET–CT dictation. Additional breast imaging studies, clinical data, and the final histopathology of the breast lesions were correlated with the PET–CT images. Of 1951 patients who underwent PET/CT, 440 incidental breast lesions were identified in 438 patients. Of these 440 lesions, 195 (45 %) were benign, 160 (37 %) malignant, and 85 (19 %) missing data. A total of 25 PBCs were diagnosed; with a median size of 1.8 cm (range 0.8–10.7 cm); and a median SUV_max of 4.4 (range 1.7–17.6). There were 19 invasive ductal cancers, 1 invasive lobular cancer, 2 papillary cancers, 1 tubular cancer, 1 sarcomatoid cancer, and 1 ductal carcinoma in situ. Eight patients had regional nodal disease. Mammography revealed the PBC in 19 of 23 tumors (83 %), sonography in 22 of 23 (96 %). Six percent (25 of 440) of incidental breast lesions identified on FDG PET–CT represent PBCs; more than half were at an early stage and potentially curable.