Sentinel node biopsy in uro-oncology: a history of the development of a promising concept

Lymph node staging is important in many urologic malignancies. The lack of a sufficiently accurate noninvasive lymph node staging modality has proven to be challenging as most urologic malignancies rely on surgical lymph node removal for regional staging. Penile cancer has been a model disease for the development of the sentinel node concept, which has subsequently been successfully adapted to breast cancer and melanoma studies. Currently, the sentinel node technique is standardized in many centers and under development for new indications. The introduction of near-infrared cameras and fluorescence techniques has paved the way for robot-assisted laparoscopic sentinel node biopsies in prostate cancer, urinary bladder cancer, and renal cancer. Fluorescence techniques have increased visual guidance towards lymph nodes during surgery and have challenged previously established templates for surgical lymph node removal. This review discusses the history of our understanding of the lymphatic system and the development of the sentinel node concept and highlights the importance of early and minimally invasive regional lymph node staging. Contemporary data on sentinel node biopsy in each of the urologic malignancies are assessed. Current trends towards robot-assisted sentinel lymph node removal are discussed, and the diagnostic accuracy and oncologic safety of sentinel node procedures are addressed. In an era of several new sentinel node indications, the importance of proper case selection, protocolled regimen, consequent follow-up, and back-up strategies in the case of radiotracer-silent or nonvisualized regions is stressed.