Diagnostic Characteristics and Clinical Relevance of Incidental Hypermetabolic Breast Lesions Detected on 18F-FDG PET-CT: A Retrospective Evaluation.

Rationale and objectives: The study aimed to evaluate demographic and radiological characteristics of breast incidentalomas found on 18-fluorodeoxyglucose Positron Emission Tomography-Computed Tomography (¹⁸F-FDG PET-CT) performed for extramammary indications.

Materials and methods: A total of 12633 ¹⁸F-FDG PET-CT scans performed between January 1, 2018 and January 1, 2024, were retrospectively reviewed. Breast incidentalomas that had undergone breast imaging, tissue diagnosis, or at least 2-year radiological follow-up were included. Demographic data and lesion size were recorded. Maximum and average standardized uptake values (SUV_max-SUV_avg) and SUV corrected for lean body mass (SUL) were calculated using region of interest (ROI).

Results: The inclusion criteria were met in 101 lesions (81 benign and 20 malignant). The most common benign lesion was fibroadenoma (n = 21), followed by stable lesions during follow-up (n = 18) and benign breast parenchyma (n = 11). The most common malignant lesion was invasive ductal carcinoma (n = 11). The diagnostic characteristics of SUV_max≥ 3, SUL_max≥ 2, SUV_avg≥ 0.735, SUL_avg≥ 0.48, and BI-RADS≥ 4 were 75%, 70%, 75%, 70% and 100% for sensitivity, 69%, 69%, 62%, 62% and 67% for specificity, and 69.3%, 68.3%, 62.4%, 61.4% and 73.3% for accuracy, respectively. The highest negative predictive values (NPV) were obtained with BI-RADS and SUV_max (100% and 92%, respectively). No significant difference in malignancy rate was observed for the lesion size and age of the patients (p > 0.05).

Conclusion: There is a risk of detecting malignancy in incidental lesions showing ¹⁸F-FDG uptake. Radiological workup must be done, but SUV_max, with a high NPV value, can be used in conjunction with BI-RADS assessment for appropriate patient selection and effective management of resources.