Incidental hip lesions on fluorodeoxyglucose-positron emission tomography during breast cancer staging: Addressing false positives in clinical practice

Introduction: Fluorodeoxyglucose-positron emission tomography-computed tomography (FDG-PET/CT) is increasingly used in breast cancer (BC) staging due to its high sensitivity for detecting extra-axillary lymph nodes and distant metastases. This hybrid imaging modality is particularly valuable for its ability to identify metastases not readily detected by conventional methods like CT and whole-body bone scan (WBBS). However, FDG-PET/CT has limitations, especially with lower-proliferative, low-grade tumors, and well-differentiated luminal BC subtypes, which may show reduced FDG uptake. Although FDG-PET/CT generally has significantly fewer false positives (FPs) than standard imaging, FPs on FDG-PET/CT can still cause patient anxiety and treatment initiation delays. Case Series: In our case series, we highlight three breast cancer patients who presented with FDG-PET/CT avid hip lesions which were reported as possible metastatic disease but on further investigation were all found to be histologically proven benign false positives (FPs). These findings underscore the need for careful interpretation, as solitary FDG-avid lesions can mimic metastatic disease, potentially leading to unnecessary anxiety, additional diagnostic procedures, and delays and significant alterations in treatment. When clinical history, examination, and imaging modalities like magnetic resonance imaging (MRI) cannot definitively diagnose a lesion, histopathological confirmation becomes crucial. Accurate diagnosis and staging, including biopsy, if necessary, are essential for determining the appropriate first-line systemic treatment for each patient. Conclusion: Ultimately, FDG-PET/CT enhances BC staging by improving detection accuracy across tumor phenotypes and grades; however, it requires careful interpretation and a multidisciplinary approach to prevent overtreatment and ensure the best patient outcomes.