Role of Axillary Lymph Node Dissection for Residual MACROMETASTASES After NEOADJUVANT Chemotherapy in Patients With HER2+ and Triple Negative Breast Cancer: The OPBC-11/MACRONAC Study

Inclusion Criteria: * Women and men with a diagnosis of stage I-III TNBC or HER2+ breast cancer at diagnosis. HER2+ is defined as an Immunohistochemistry (IHC) score of 3+ or positive FISH. TNBC is defined as ER and Progesterone Receptor (PR) IHC expression of 0 and HER2 negativity defined as either IHC expression of 0-1+ or lack of gene amplification (FISH \< 2.0). Patients with ER low (1-10%) and/or PR low (1-10%) tumors are allowed. * Any histological subtype * For Clinical Nodal Stage (cN) 0 at presentation: any axillary staging technique including palpation with or without imaging is allowed. Dual tracer mapping is not required for SLN surgery. * For cN+ at presentation: Percutaneous biopsy proven confirmation is required at diagnosis. Staging techniques after NAC include: SLN surgery with dual mapping or Targeted Axillary Dissection (TAD: imaging-guided localization of sampled node in combination with SLN procedure with or without dual mapping) or Tailored Axillary Surgery (TAS: removal of the sentinel lymph nodes as well as selective removal of all palpable disease and documentation of the removal of the initially biopsy-proven and clipped lymph node metastasis by specimen radiography) or the MARI procedure (Marking Axillary Lymph Nodes with Iodine Seeds). * Received neoadjuvant chemotherapy * Residual macrometastases (metastasis greater than 2 mm in diameter) detected on SLN surgery or TAD ot TAS or MARI (on frozen section or final pathology) * Concomitant presence o…