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Breast Imaging

E2209. Ultrasound Evaluation of Internal Mammary Lymph Nodes: Diagnostic and Therapeutic Considerations

Gu C,  Glazebrook K,  Hieken T,  Anderson T. Mayo Clinic, Rochester, MN

Address correspondence to C. Gu (gu.chris@mayo.edu)

Background Information: Internal mammary (IM) lymph node metastasis occurs in upwards of 20% of all patients with primary breast cancer. Some studies have shown that IM nodal metastasis confers an unfavorable prognosis regardless of axillary nodal status. In addition, studies have shown that adjuvant regional nodal irradiation including IM fields improves oncologic outcomes for select patients. Evaluation of IM nodes by ultrasound in patients with either known breast cancer or a new diagnosis of breast cancer can guide radiologists in obtaining a cytopathologic diagnosis. We present an overview of the role that IM nodes play in breast cancer staging and examples of normal and abnormal IM nodes on ultrasound. In addition, we discuss the approaches, techniques and pitfalls in performing ultrasound-guided fine needle aspiration (FNA) of IM nodes.

Educational Goals/Teaching Points: The goals of this exhibit are to review the implications of detecting IM node involvement on breast cancer staging and review therapeutic implications of IM nodal disease at presentation (systemic therapy and adjuvant radiation). In addition, we illustrate the ultrasound appearance of normal versus metastatic IM nodes and correlate with MRI and PET/CT findings and discuss approaches, technical considerations, and pitfalls in performing ultrasound-guided FNA of IM nodes.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques: Normal IM lymph nodes are between the first and sixth intercostal spaces and typically have an ovoid appearance on ultrasound. Although variable, most normal IM lymph nodes are less than 1 cm in size. We will review the typical imaging appearance of both benign and malignant IM lymph nodes on ultrasound through a series of cases and include MRI and PET/CT corollary for malignant nodes. Through static images and video clips, we will discuss the technical considerations in performing ultrasound-guided FNA of IM nodes, including needle position and identification of surrounding vessels. Finally, we will review tumor, node, and metastasis staging of breast cancer as it relates to IM nodal involvement and its implications to therapy, including alterations to neoadjuvant chemotherapy and adjustments to postmastectomy radiation portals.

Conclusion: Ultrasound has become an increasingly powerful and popular modality in the evaluation of IM lymph nodes. Accurate and confident assessment of benign and malignant nodes, including ultrasound-guided FNA, is helpful for the management of select cases of newly diagnosed breast cancer with therapeutic and prognostic implications for patients.