Axillary lymph node dissection is not routinely indicated in patients with sentinel lymph node residual micrometastases following neoadjuvant systemic therapy.

[BACKGROUND] The clinical relevance of residual micrometastatic nodal disease (ypN1mi) detected in the sentinel lymph node (SLN) or following targeted axillary dissection (TAD) after neoadjuvant systemic therapy (NST) remains uncertain, particularly regarding the need for completion axillary lymph node dissection (cALND).

[METHODS] This narrative review summarizes evidence from registry-based and international cohort studies evaluating axillary recurrence and oncological outcomes in patients with ypN1mi managed with or without cALND after NST.

[RESULTS] Analyses from the SEER registry and the OPBC-07/microNAC cohort demonstrate a low incidence of axillary recurrence and no significant differences in oncological outcomes between SLNB alone and cALND. In subgroup analyses of triple-negative breast cancer, microNAC reported lower axillary recurrence rates with cALND; however, no difference in invasive recurrence was observed between groups.

[CONCLUSIONS] Routine cALND appears unnecessary in most patients with ypN1mi after NST. Future studies should evaluate whether regional nodal irradiation can also be safely omitted.