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Breast Imaging

E2377. A Case-Based Review of Uncommon Causes of Axillary Adenopathy and Potential Pitfalls in Management

Russell T,  Madireddi S,  Costello J. San Antonio Uniformed Services Health Education Consortium, Fort Sam Houston, TX

Address correspondence to T. Russell (timothy.g.russell16.mil@mail.mil)

Background Information: Axillary adenopathy is a common clinical scenario encountered in daily radiology practice. Defining an abnormal axillary lymph node can be challenging on all radiologic modalities. Appropriate management can also be problematic, with several potential pitfalls regarding unilateral and bilateral clinical presentation. The purpose of this educational exhibit is to review the key imaging features of axillary adenopathy, with application of current management guidelines, based upon institutional experience and the BI-RADS version 5 manual. A case-based review of common and uncommon causes of axillary adenopathy will also be presented, with radiology-pathology correlation. Our goal is to improve background knowledge for the general radiologist and physicians in training, so that patients presenting with axillary adenopathy are managed more effectively.

Educational Goals/Teaching Points: The goals of this exhibit are to understand the anatomy and physiology of normal axillary lymph nodes and recognize key ultrasound, CT, mammographic, and MRI features of abnormal axillary lymph nodes using a case-based review of causes of axillary adenopathy, with radiology-pathology correlation. We also aim to understand appropriate clinical management of unilateral and bilateral axillary adenopathy and review potential mimickers of axillary adenopathy.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques: Axillary lymph node levels are categorized in relation to the pectoralis minor muscle, and abnormal axillary lymph nodes are best defined based upon imaging morphology. Key imaging features include concentric or focal cortical thickening, fatty hilum compression or displacement, and round rather than reniform shape. There are no specific size criteria for abnormal axillary lymph nodes, although when greater than 2 cm in the longest dimension, the reader should look closely for cortical thickening or fatty hilar effacement. If present, lymph node calcification may be helpful in determining cause. Axillary adenopathy differential considerations and clinical management depends on whether findings are unilateral or bilateral. For unilateral axillary adenopathy, an underlying breast mass must be excluded, and lymph node biopsy or breast MRI may be indicated, depending on clinical context. For bilateral axillary adenopathy, initial management should be focused towards determining potential systemic causes. Uncommon causes of axillary adenopathy include tattoo pigment, gold injection, or silicone uptake.

Conclusion: Axillary adenopathy is a frequently encountered clinical scenario in diagnostic breast imaging. Morphology is the key imaging feature to identify abnormal axillary lymph nodes. Knowledge of normal anatomy, differential considerations, and awareness of potential pitfalls in management are essential to providing appropriate clinical care. Comparison to the contralateral axilla can be helpful to identify pathologic axillary lymph nodes, particularly in a patient with underlying systemic disease process. Potential mimickers of axillary adenopathy include axillary tail mass and schwannoma.