Background: Invasive lobular carcinoma (ILC) comprises 10-15% of new invasive breast cancers in the United States, and is associated with older age, more advanced stage, and higher nodal positivity compared to invasive ductal carcinoma (IDC). Although ILC is far less common than IDC, it is disproportionately represented in false negative screening mammograms. This is attributable to the loss of E-cadherin, which allows the cells to grow in single file. ILC is mammographically occult in 19-43% of cases. Ultrasound (US) and notably magnetic resonance imaging (MRI) have a higher sensitivity than mammography with the caveat that ILC nodal metastases may be very subtle on US and MRI. Contrast enhanced digital mammography (CEDM) also shows great promise in detecting ILC. ILC is commonly Luminal A subtype with high estrogen receptor (ER) and progesterone receptor (PR) expression, and it rarely demonstrates human epidermal growth factor receptor 2 (HER2) amplification. Due to ILC’s high rate of ER positivity, F-18-fluoroestradiol (F-18 FES) positron emission tomography/computed tomography (PET/CT) may more accurately identify ILC metastases and recurrences than F-18-fludeoxyglucose (F-18 FDG) PET/CT. Our case-based educational exhibit will discuss these unique pathologic and imaging characteristics, diagnostic challenges, and how the combination of clinical history and imaging can significantly improve detection and aid in diagnosis of ILC.
Learning Objectives: 1. Review the unique pathologic and imaging characteristics of ILC. 2. Illustrate the advantages and challenges of detecting ILC with different imaging modalities. 3. Highlight the evolving role of F-18 FES PET/CT in the detection of otherwise occult metastatic ILC, especially as it compares to F-18 FDG PET/CT.
Abstract Content/Results: A series of approximately 10 ILC cases will be shared, including presentation, diverse appearance, diagnosis, and false negatives on all imaging modalities (mammography, ultrasound, and magnetic resonance imaging). In addition, several cases will include F-18 FES PET/CT in comparison with more traditional F-18 FDG PET/CT.
Conclusion: Our educational exhibit will help radiologists understand imaging modality strengths and limitations in diagnosing ILC and showcase the utility of F-18 FES PET/CT compared to F-18 FDG PET/CT studies.
