The Performance of Contrast Enhanced Mammography in the Determination of the Extent of Disease in Invasive Lobular Carcinoma

Purpose: ILC comprises 5-15% of invasive breast cancer and can be difficult to diagnose on conventional imaging (Mammogram and US). CEM (± Tomosynthesis) improves ILC visualization. This study aims to show the performance of CEM in determining extent-of-disease in ILC.

Methods: This was a retrospective, single-center study, approved by the institutional review board, which waived the need for informed consent.

All CEM examinations of ILC performed at our institution between 2016-2020 were included. Patient demographics and results were retrieved from digital records. Lesion size was defined as the longest diameter.

Results: Twenty women were included, with an average age of 74 years (SD 10.4, range 51-87). The main indication for CEM was to determine extent-of-disease.

Breast density was rated according to BI-RADS. Most of the patients were grades B (44.4%) and C (50%).

56% of the imaging had mild BPE, 39% minimal, and 5% moderate.

All lesions were either a mass (72.2%) or a non-mass enhancement (27.8%).

Seventy percent of biopsies were pure ILC, the rest being mixed. All were ER+ and Her2-. Seventy-five percent were PR+. Median Ki-67 index was 10% (range 1-30%).

Average imaging lesion size was 28.5mm (SD 26.9). At pathology, the average diameter was 22mm (SD 18.8). The Pearson correlation coefficient (0.78) indicates that CEM overestimates size within reasonable limits.

Conclusion: ILC requires contrast imaging due to its multicentricity and bilaterality. Breast MRI is more expensive, less accessible, and has lower specificity, requiring additional workup. CEM has higher specificity and significantly correlates with pathology at surgery. Therefore, CEM is very accurate, feasible, and requires much less additional workup.