Axillary Staging of Breast Cancer: What the Radiologist Should Know

Abstract

Identifying the presence of axillary node and internal mammary node metastases in patients with invasive breast cancer is critical for determining prognosis and for deciding on appropriate treatment. Sentinel lymph node biopsy (SLNB) is the definitive method to exclude axillary metastases. Patients with positive SLNB results generally undergo axillary lymph node dissection (ALND). The benefit of preoperative identification of axillary metastases is that it allows the surgeon to proceed directly to ALND and to avoid an unnecessary SLNB and the need for a second surgical procedure involving the axillary nodes. Knowledge of the important anatomic landmarks of the axilla is important in finding and accurately reporting suspicious lymph nodes. The pathologic features of nodal metastases illuminate the imaging appearances of these nodes, as depicted with all modalities. Ultrasonography (US) is the primary imaging modality for evaluating axillary nodes. Morphologic criteria, such as cortical thickening, hilar effacement, and nonhilar cortical blood flow, are more important than size criteria in the identification of metastases. US-guided lymph node sampling, especially with core biopsy, is invaluable in confirming the presence of a metastasis in a suspicious node. Core biopsy has been shown to be equal in safety to fine needle aspiration and has a significantly lower false-negative rate. Magnetic resonance imaging is also useful, with the added benefit of providing a global view of both axillae. Computed tomography and radionuclide imaging play a lesser role in imaging the axilla. Preoperative image-based identification and sampling of abnormal lymph nodes that have a high positive predictive value for metastases is an extremely important component in the management of patients with invasive breast cancer.

Role of Sonography for the Locoregional Staging of Breast Cancer

“…SLNB was developed as a less invasive procedure to surgically stage the axilla; it allows more rigorous pathologic evaluation of fewer nodes removed and is associated with less morbidity than ALND [42]. SLNB has a low false-negative rate [32] and is now routinely performed for patients with clinically node-negative invasive breast cancer. If SLNB reveals no metastatic axillary nodal disease, no further axillary surgery is needed, and patients are spared the morbidity associated with ALND.…”

“…Most breast lymphatics drain to the ipsilateral axillary nodes, and the axilla is the most common site for nodal metastases from breast cancer. The presence or absence of axillary nodal disease is an important prognostic indicator in patients with breast cancer [31,32].…”

Role of Axillary Ultrasound, Fine Needle Aspiration Cytology and Sentinel Lymph Node Biopsy in clinically N0 Breast Cancer

“…Axillary lymph node which was oval, smooth, with well-defined margin, hypoechoic, with uniformly thin cortex measuring 3 mm or less was considered as benign. Nodes with any of the features like diffuse cortical thickening, focal cortical bulge, eccentric cortical thickening, complete or partial effacement of the fatty hilum, complete or partial replacement of the node with an ill-defined or irregular mass, and micro-calcifications in the node was considered as suspicious on imaging [6]. Figure 2 shows the sonological images for suspicious lymph nodes.…”

“…Now SLNB has emerged as an equally effective method of evaluating axilla in cases of early stage breast cancer because of significantly lower rate of morbidity than does ALND [4][5][6].…”

Comparative study between ultrasound-guided fine needle aspiration cytology of axillary lymph nodes and sentinel lymph node histopathology in early-stage breast cancer

“…For almost a century, radical mastectomy plus axillary lymph node dissection, introduced by Halsted in 1882 until the 1970s of the 20th century (6), was the standard surgical treatment for all breast tumor stages, resulting in serious complications in the upper limb ipsilateral to surgery (7)(8)(9)(10)(11).…”