Anatomy and Physiology of Lymphatic Circulation: Application to Lymphatic Mapping

The lymphatic system is a field of continuing interest in oncology, both because of its role in the immune system and because it constitutes a major route of dissemination of cancers. Studies of its anatomy conducted over several centuries have demonstrated a complex network of ducts and lymph nodes throughout the body and revealed clinically relevant aspects. The anatomical concept of lymphatic drainage from a specific site of interest evolved from predictable routes to a highly variable pattern depending on anatomical variations, potential connections to major and minor surrounding lymphatic basins and physiological changes such as pressure gradients, age and prior surgical interventions. In the past, anatomists made their observations at a macroscopic level in cadavers. Recent progress in imaging contributed to further unravelling of this intricate system. Current lymphoscintigraphy techniques and recent developments enabling fluorescence lymphography with indocyanine green and quantum dots have allowed the visualisation of normal physiological drainage patterns down to a microscopic level, even from several primary sites simultaneously. Knowledge of the anatomy and physiology of the lymphatic system forms the basis of the sentinel lymph node concept. Sentinel lymph node biopsy as a staging procedure has revolutionised surgical approach for melanoma, breast cancer and various other malignancies, and is at the brink of playing a major role in the selection of patients for adjuvant systemic therapy.