Objective: To evaluate the significance of incidentally discovered breast lesions on 18-fludeoxyglucose ((18)F-FDG) positron emission tomography (PET)/CT.
Methods: 6050 (18)F-FDG PET/CT studies, performed between January 2009 and February 2012, were retrospectively reviewed. 55 lesions in 50 patients were identified. Additional work-up, including mammography, ultrasound, follow-up (18)F-FDG PET/CT and biopsy, was available for 39 incidental breast lesions in 36 patients. All patients were female, with mean age 61.5 years (range 36-90 years). The maximum standardised uptake value (SUVmax), CT size and CT Breast Imaging Reporting and Data System (BI-RADS®) scores were compared between the malignant and the benign subgroups, using the unpaired t-test and Fisher's exact test. Tests were two-sided and a p-value of <0.05 was considered to be significant.
Results: Incidental breast lesions were identified in 50 (0.8%) of 6050 (18)F-FDG PET/CT studies. 21 (53.8%) of the 39 breast incidentalomas were malignant on biopsy or imaging, of which 15 (38.5%) represented a second primary breast cancer. A statistically significant difference in the mean SUVmax between malignant and benign breast lesions was observed (p=0.021). Malignancy was significantly more common in the CT BI-RADS Category 4 or greater groups (76.2%; p=0.0105).
Conclusion: Incidental breast lesions detected at (18)F-FDG PET/CT are uncommon. When detected, however, they may represent malignancy in up to 53.8% of cases.
Advances in knowledge: SUVmax and CT findings at (18)F-FDG PET/CT can assist with differentiating benign and malignant breast conditions, guiding further evaluation with dedicated breast imaging. Review of (18)F-FDG PET/CT-detected breast lesions by a breast radiologist may be helpful in determining the need for and correlation with further breast imaging. Radiologists and nuclear medicine physicians should be cognisant of breast pathology when reporting (18)F-FDG PET/CT image data sets.