Location of sentinel lymph nodes in patients with cutaneous melanoma: New insights into lymphatic anatomy

Background: Accurate staging of melanoma patients by sentinel node (SN) bio psy can be achieved only if all SNs draining a given melanoma site are iden tified and removed for detailed histologic examination. Lymphoscintigraphy with a radiolabeled colloid provides an objective and reliable method of lo cating SNs and demonstrates that confident prediction of their location is not possible on clinical grounds. Study Design: Lymphatic drainage pathways demonstrated by preoperative lymp hoscintigraphy for 1,759 patients with primary cutaneous melanomas were rev iewed, and locations of SNs in these patients were documented. An SN was de fined as any node receiving direct lymphatic drainage from a primary melano ma site. Results: In many instances the cutaneous lymphatic drainage pathways were f ound to be at variance with longheld concepts of lymphatic anatomy. Several new pathways were identified, draining to SNs in unexpected sites. These i ncluded triangular intermuscular space SNs (from upper back and, rarely, up per limb primaries), paraaortic and retroperitoneal SNs (from upper and low er back primaries), and costal margin SNs with onward drainage to internal mammary nodes (from periumbilical primaries). Occasional drainage to node f ields on the opposite side of the body was noted from head, neck, and trunk primaries, and drainage to interval nodes (by definition, SNs) outside rec ognized lymph node fields was also observed. Conclusions: Knowledge of the possibility of these unusual lymphatic draina ge patterns and SN sites should help to ensure the accuracy and completenes s of SN identification. Preoperative lymphoscintigraphy to definitively loc ate SNs is recommended for every patient undergoing an SN biopsy procedure. (J Am Coll Surg 1999;189:195-206. (C) 1999 by the American College of Surg eons).