Sentinel Lymph Node in Early Breast Cancer: Evidence, Techniques, and Controversies

The lymphatic system has historically been established as a network of vessels that works complementary to the cardiovascular system by draining the extravasated fluid from the interstitium [1]. In tumors, the lymphatics act as a conduit for transport of tumor cells to regional nodes, which in turn might facilitate systemic seeding [2]. The biological understanding of breast cancer has progressed from a purely “mechanistic model” (forming the basis of Halstedian radical resections) to Fisher’s “systemic model” (forming the basis of systemic therapy in breast cancer), and finally to “spectrum model” [3, 4]. With the evolution of evidence, the surgical management of breast cancer has been tailored from radical/supra-radical surgeries to ultra-conservative approaches. Regional management of breast cancer has also evolved with sentinel lymph node biopsy (SLNB) becoming the “evidence-based standard” in clinically appropriate settings. In this chapter, we will trace the evolution and incorporation of SLNB in early breast cancer.