Axillary dissection (AD, removal of all lymph nodes at levels 1–2 of the axilla) was the standard procedure for local control and axillary staging until sentinel node biopsy (SNB) was imported from melanoma surgery and introduced to breast surgery in the 1990s by Krag and Giuliano [1,2]. SNB consists of peritumoral or periareolar injection of patent blue or a radiopharmaceutical for subsequent retrieval of the marked lymph node in the axilla [3]. It is long known that SNB causes less morbidity than axillary dissection, in terms of lymphedema, length of surgery, length of hospitalization, change in sensation, and quality of life [4,5].

The theoretical risks of SNB are that other positive nodes remain untreated, and the missed nodes will understage the axilla, so that the patient might miss important subsequent treatments, like nodal radiotherapy, targeted systemic therapy, salvage therapy and genomic testing [[6], [7], [8], [9], [10], [11]].

SNB has been established as an acceptable alternative to AD in patients with early, node-negative breast cancer. An unpublished metanalysis, presented in 2023 at San Antonio, concludes that “less axillary surgery” (SNB in recent trials and various degrees of axillary sampling in older trials) provides comparable survival outcomes as AD [12]. There is also a 2017 Cochrane metanalysis, which considered that moderate-quality evidence favors SNB against AD, but that the combination of newer and older trials provides lower rates of survival for less axillary surgery [13]. While the overarching conclusions of the historical trials are widely recognized, the nuances and application of these findings in complex clinical scenarios, such as those involving T3 and T4 tumors, extranodal disease, and post-neoadjuvant surgery, often remain a source of debate and require further elucidation.

Therefore, it is still necessary to select the “right patients” eligible for “less axillary surgery”. The purpose of this study is to provide an easy historical review about SNB in breast cancer, focused on inclusion criteria and survival outcomes.