Breast incidentalomas on 18-Fluorodeoxyglucose positron emission tomography-computed tomography performed for a non-mammary cause: Significance and outcomes

Introduction: The aim of the study was to determine the rate of malignancy in breast incidentalomas found on 18-Fluorodeoxyglucose Positron Emission Tomography-Computed tomography (18 FDG PET-CT) performed for non-mammary causes and evaluate outcomes. Methods: A single-centre, retrospective review of 5728 18-FDG PET-CT scans performed between January 1, 2017 and April 30, 2019 was undertaken. Cases with known primary breast cancer or metastases to the breast in the previous ten years were excluded. Diagnosis was confirmed with breast imaging, histology and 2-year follow-up. Data analysed included age, the pattern of uptake on 18-FDG PET-CT, lesion size and BIRADS score. Results: Thirty-two Breast incidentalomas were identified in 27/5728 scans (0.47%). 18 lesions (56.3%) were malignant. Five underwent curative surgery. Nine lesions (28.1%) were benign and five (15.6%) were false positive. Conclusion: Breast incidentalomas are uncommon on 18-FDG PET-CT but require work-up for malignancy. BIRADS score has a high sensitivity and specificity for malignancy in18-FDG PET-CT incidentalomas but age, size of the lesion and the pattern of uptake on 18-FDG PET-CT were not useful in differentiating benign from malignant incidentalomas.