Abstract and Introduction
Objectives Management of the axilla in breast cancer patients has evolved considerably since the introduction of the sentinel lymph node (SLN) biopsy in the 1990s. Several new clinical and technological developments in the last decade warrant special consideration due to their impact on pathology practice.
Methods This review covers the SLN biopsy procedure, issues in the histopathologic and molecular diagnosis of the SLN, and most importantly, evidence from recent practice-changing clinical trials.
Results ACOSOG Z0011, IBCSG 23–01, and AMAROS trials have shown that early-stage breast cancer patients who have limited metastatic involvement of the SLNs do not benefit from completion axillary dissections.
Conclusions It is not necessary for pathologists to search for all small metastases to predict non-SLN involvement, regional recurrence, or death due to disease. Processing should be designed with the goal of detecting macrometastases. Multiple levels, routine immunohistochemistry, and molecular testing are not recommended.
Treatment of the lymph nodes in the axilla of women with breast cancer has evolved considerably over the past century, especially within the past two decades. Historically, axillary lymph node clearance was the surgical approach in all patients with breast cancer. This surgery is associated with a risk of complications, including lymphedema, pain, numbness, and impaired mobility of the arm. As most patients with early-stage breast cancer have tumor-free nodes, it was apparent that many patients were overtreated by this approach.
Sentinel lymph node (SLN) biopsy was developed in the 1990s and soon thereafter became the standard of care in the surgical management of patients with clinically node-negative breast cancer. This procedure is based on two principles: first, there is a predictable pattern of lymphatic drainage to the regional lymph node basin, and second, the first-order lymph nodes ("sentinel lymph nodes") act as an effective filter for tumor cells. The SLN status is used to predict the involvement of additional axillary lymph nodes and to identify a subset of patients who can be spared from extensive surgery.
At least seven randomized controlled trials (RCTs) (NSABP B32 and Sentinella/GIVOM are the largest) have compared SLN biopsy with axillary lymph node dissection (ALND) in clinically node-negative patients. These trials confirmed that there is no significant difference in disease-free survival (DFS) or overall survival (OS) in patients who had SLN biopsy alone vs ALND. Also, in those who underwent SLN biopsy alone, the risk of lymphedema and neurologic deficits was significantly reduced.
ALND was initially omitted only in patients with negative SLNs. Recently, practice-changing trials have indicated that it also can be safely omitted in patients who have limited metastatic involvement of the SLNs, as there is no clinically significant survival benefit from completion ALND in this setting.[5,6] Moreover, there is minimal benefit to finding small (<0.2 mm) or occult metastases in SLNs.[7,8] These results have had an impact on the multidisciplinary care of patients with breast cancer, including the practice of pathology.
This review will cover the evidence behind recent changes and the current recommended practice in evaluation of axillary lymph nodes in patients with breast cancer.
Am J Clin Pathol. 2018;150(1):4-17. © 2018 American Society for Clinical Pathology