Background: Scientific efforts aim at a reduction of axillary morbidity through reduced axillary intervention among patients with early breast cancer. However, it is still unclear if this approach is feasible in all subtypes based on their risk of axillary involvement. We analyzed the association of tumor biology and occult axillary involvement with data from arms A and B of the SENTINA trial (Kühn T et al., Lancet Oncol 2013). Methods: Patients were included if they presented with a clinically negative axilla before NAT (arms A and B) and stratified according to tumor biology. All patients received SLNB before NAT, in cases of negative SLNB without further axillary surgery (Arm A) and in cases of positive SLNB (Arm B) with SLNB and axillary dissection after NAT. Logistic and linear regression analyses were carried out to evaluate the association between tumor biology and axillary involvement before and after NAT. Results: Of the 1022 patients in arms A and B of the SENTINA trial 926 were evaluable for this analysis. Of these, 27.9% had triple negative (TN), 16.3% hormone receptor (HR) and HER2 positive (triple positive = TP), 47.6% HR positive and HER2 negative (luminal) and 8.2% HR negative and HER2 positive (HER2) tumors. 39.7% of the luminal, 28.9% of the HER2, 19% of the TN and 47% of the TP tumors had involved SLN before NAT. Subgroup comparisons showed a significant difference between luminal and TN (p < 0.0001), whereas the differences between luminal and TP (p = 0.115) and HER2 (p = 0.077) were not statistically significant. The 317 patients with involved SLN prior to NAT received SLNB and axillary dissection after completion of NAT. The analysis after NAT showed trends for lower rates of involved lymph nodes for the high-risk groups (TN 20% / TP 14.3% / HER2 8.7%) compared to luminal tumors (27.6%) without reaching statistical significance. Conclusions: Our analysis demonstrates that among patients enrolled in the SENTINA trial, patients with triple negative disease have the lowest risk for occult lymph node metastases at initial presentation. Our results do not justify more intense local intervention among patients with triple negative breast cancer.