Heterogeneous Responses of Axillary Lymph Node Metastases to Neoadjuvant Chemotherapy are Common and Depend on Breast Cancer Subtype

Background The objective of this study was to analyze heterogeneous responses of axillary lymph node metastasis to neoadjuvant chemotherapy and to determine to what extent they differ between tumor subtypes (TN, HER2+, HR+/HER2−). Methods This retrospective, monocenter study included 72 consecutive, histologically node-positive breast cancers (cT1–4 cN1–3 cM0) diagnosed in the period from January 2015 to December 2016, who had received axillary lymph node dissection following neoadjuvant chemotherapy. All individual lymph node specimens were re-evaluated for the presence of tumor cells and chemotherapy effects to assess their response to neoadjuvant chemotherapy on an individual lymph node level according to the Sataloff classification. Results Heterogeneous axillary responses to neoadjuvant chemotherapy occurred in 47.2% of the included 72 patients. The partial response rate was significantly higher in HR+/HER2− tumors (74.2%) than in TN (28.6%) and HER2+ tumors (25.0%) ( p