Incidental diagnosis of breast cancer in FDG PET/CT: Frequency in 1283 patients

Objectives The sensitivity of FDG PET in the incidental detection of breast cancer (BC) is not well established. We evaluated the frequency of incidental detection of BC in routine FDG PET/CT of cancer patients with no history of BC.

Methods Retrospectively, we reviewed reports from FDG-PET/CT scans of 1283 female patients ages 28-90 with no previous history of BC. Cases with incidental focal FDG uptake in the breast suggestive of BC were recorded. The presence or absence of BC was assessed using all available clinical and pathologic follow-up.

Results PET/CT scans revealed an incidental finding of focal FDG uptake in the breast in 20 (1.6%) of the 1283 cases. Of those 20 patients: 5 (25%) had no follow-up data; 7 (35%) had false-positive findings, and primary BC lesions were confirmed by biopsy and/or mammography in 8 (40%). The biopsy proven BC lesions had a mean size of 1.3 cm (range 0.8-1.8 cm; median 1.4 cm) and mean SUVmax 4.2 (range 1.6-18.6; median 2.5). Pathology included infiltracting ductal carcinoma in 7/8 (88%) and ductal carcinoma in-situ in 1/8 (12%). Of the 8 cancer patients, mammography was performed on 6 patients; 4/6 (67%) with a BI-RADS 5 lesion and 2/6 (33%) with a BI-RADS 4 lesion. The 7 false positive lesions had a mean size of 1.3 cm (range 0.6-1.9 cm; median 1.5 cm) and mean SUVmax 2.1 (range 1.1-5.7; median 1.3). A punch biopsy was performed on 1 patient revealing an intramammary lipoma.

Conclusions We conclude 1.6% of female patients greater than 28 years with no history of BC had an incidental focal FDG uptake in the breast on PET/CT exam. When present, this FDG uptake represented a new, unexpected BC in at least 8/20 (40%). Therefore, an incidental finding of focal FDG uptake in the breast requires further investigation. The relationship between SUV, mammographic and MRI findings in the incidental BC cases is being evaluated