Extranodal Tumor Deposits in the Axillary Fat Indicate the Need for Axillary Dissection Among T1–T2cN0 Patients with Positive Sentinel Nodes

The American College of Surgeons Oncology Group (ACOSOG) Z0011 trial demonstrated the safety of omitting axillary lymph node dissection (ALND) in T1–T2cN0 patients with fewer than three positive sentinel nodes (SLNs) undergoing breast-conservation therapy. While microscopic extracapsular extension (mECE) > 2 mm is associated with increased nodal burden, the significance of extranodal tumor deposits (ETDs) in the axillary fat is uncertain. Consecutive patients with T1–T2cN0 breast cancer undergoing sentinel node biopsy and ALND for SLN metastases from January 2010 to December 2018 were identified. ETDs were defined as intravascular tumor emboli or metastatic deposits in the axillary fat. Clinicopathologic characteristics and nodal burden were compared by ETD status. Among 1114 patients, 113 (10%) had ETDs: 81 (72%) were intravascular tumor emboli and 32 (28%) were soft tissue deposits. Patients with ETDs had larger tumors (median 2.2 vs. 2.1 cm; p = 0.033) and more often had mECE (83% vs. 44%; p