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Objective:
MRI of the breast is a sensitive imaging modality that can detect early breast and axillary abnormalities. This study aims to improve the specificity of breast MRI in the evaluation of axillary lymph nodes, particularly in the face of continuously increasing imaging volumes, including a high rate of axillary second look ultrasounds (SL-US) performed at this institution for improved morphologic characterization of lymph nodes, with questioned increased prominence on breast MRI. This study specifically examined SL-US performed after an abnormal axillary lymph node was identified on breast MRI, with the goal of discerning whether the need for additional imaging can be reduced.

Materials and Methods:
Retrospective chart review was performed for a total of 314 patients, including women of all ethnicities over the age of 18 who underwent a breast MRI at this institution between January 1, 2018 and August 31, 2020, followed within 2 months by an axillary SL-US. MRI indication and patient demographic information such as age, breast cancer risk factors, history of current or prior breast cancer, and relevant medical history were collected and analyzed. Exclusion criteria included any axillary ultrasound not performed based off an MRI recommendation or if the axilla mentioned on breast MRI had current known biopsy-proven malignant involvement. After applying the exclusion criteria, the final SL-US total reached 204. US findings and measurements, as well as pathologic data from any subsequent percutaneous and/or surgical biopsy of these axillary lymph nodes, were included for analysis. The concordance of these results with imaging findings was documented.

Results:
Of 204 axillary SL-US examinations performed, 91 demonstrated no axillary lymphadenopathy (benign, 44.6%), 111 demonstrated abnormal lymph nodes requiring further workup (suspicious, 54.4%), and two demonstrated an alternate cause (such as silicone lymphadenopathy) for the lymph node appearance on MRI (other, 1%). Of the 111 suspicious nodes, 63 were biopsied percutaneously, with benign pathology (56.7%). Statistical analysis using an integrated multivariate model will be performed between the benign and abnormal US cohorts.

Conclusion:
By evaluating axillary SL-US findings in the context of specific clinical and imaging findings, we aim to decrease false positive axillary node abnormalities on breast MRI and improve radiologists’ awareness of patient and study specific factors that would increase its PPV. Given the frequent overestimation of lymph node size on breast MRI in our current system, this would enhance our breast imaging practice by improving patient care, reducing unnecessary healthcare spending, and optimizing diagnostic breast imaging appointment availability.