National guidelines recommend that the SLNB procedure be considered for patients with T1b tumors and above, as well as T1a tumors with high-risk features, based on an expected risk of SLN positivity exceeding 5%. This 5% risk threshold is based on the SLNB false negative rate observed in the Multicenter Selective Lymphadenectomy Trial (MSLT-I; Morton 2014), which showed that the SLNB procedure had no impact on survival. Use of this threshold results in an overall rate of SLNB positivity of approximately 12% (Ellis 2010; Bamboat 2014; Joyce 2017).
