Axillary Lymphadenectomy

Technical Aspects of Sentinel Node Biopsy

Sentinel node biopsy is accurate with lumpectomy or mastectomy. Radiolabeled particles and/or blue dye are injected adjacent to the tumor or in a subdermal, periareolar location, and the breast is lightly massaged to enhance dye transit. A gamma probe is used to identify the location of radiolabeled sentinel nodes and guide incision placement. Radioactive or blue-stained nodes and lymphatics are identified by inspection within axillary fat.

Sentinel nodes identified by dye uptake are excised for pathology analysis. Dye uptake may be reduced in nodes replaced by tumor or when afferent lymphatics become plugged by tumor emboli, leading to false-negative (FN) sentinel node mapping. Careful intraoperative palpation of axillary tissue can identify suspicious firm or enlarged nodes for excision and testing and can reduce FN rates.

Frozen section analysis intraoperatively allows completion axillary dissection during the same surgical procedure for positive nodes. Complete histologic analysis includes serial sectioning of the sentinel nodes with three to five sections per node examined. Many centers also add immunohistochemical staining for breast epithelial cytokeratins to facilitate identification of small tumor deposits. Axillary node metastases are classified by size as macrometastases (over 2 mm, N1), micrometastases (0.2 to 2 mm, N1mic), and isolated tumor cells (ITCs, N0[i+]), with prognosis inversely proportional to the size of the metastatic deposit.

Sentinel node mapping appears reliable in the majority of clinical situations, including in patients with prior biopsies, biopsy site seromas, and large or multifocal primary tumors. Repeat node mapping is possible after prior axillary SNB or dissection, with lower rates of mapping success, but reliable results, if a new sentinel node is identified.

SNB is contraindicated in patients with inflammatory carcinoma because results are unreliable, most likely because lymphatic tumor deposits impede dye mapping. It is also not appropriate for patients with clinically positive axillary or supraclavicular nodes, as nodal status is already known, or for patients with distant metastases, where axillary node status is irrelevant.

Ultrasound-Guided Axillary Node Biopsy

Axillary ultrasound is being used with increasing frequency for preoperative evaluation of axillary nodes and to guide fine needle biopsy for suspicious nodes. Patients with positive fine needle node biopsies may proceed directly to axillary dissection or neoadjuvant systemic therapy without sentinel node mapping. SNB is still required if the needle biopsy is negative, as axillary fine needle biopsy has a significant FN rate.

Management of a Positive Sentinel Node

Approximately 40% to 50% of all patients with a positive sentinel node will have additional positive nonsentinel axillary nodes. Since breast cancer staging and resulting adjuvant treatment recommendations are based on the total number of involved axillary nodes, completion axillary dissection is generally indicated when a sentinel node is positive.

Completion axillary dissection remains the standard of care of patients with sentinel node macro­metastases and micrometastases, as these patients are at moderate to high risk for additional positive nodes. However, completion axillary dissection is often omitted for patients whose sentinel nodes contain only isolated tumor cells, because the risk of additional positive nodes is fairly low. Predictive models, such as the nomogram designed by Van Zee and colleagues, which estimates risk of additional positive nodes based on features of the primary tumor and sentinel nodes, may be useful in deciding whether completion axillary dissection is indicated.

Clinical trials addressing the use of axillary radiation, rather than completion dissection, have been conducted with results being evaluated.