R ECENT INTEREST and enthusiasm for lymphoscintigraphy, the imaging of flow through lymphatic vessels to lymph nodes, has accelerated as popularization of the sentinel node concept has taken hold. In 1977, the sentinel node concept was articulated by Cabanas ~ as he applied it to the surgical management of cancer of the penis. Morton et al 2 successfully applied the sentinel node concept to staging melanoma using isosulfan blue dye to visualize the path of lymph flow from the tumor site to regional lymphatic drainage basins. Later, Alex and Krag 3 investigated use of radiotracers for lymphatic mapping and sentinel node identification. Published reports 4-7 have demonstrated that images commonly identified unexpected lymphatic drainage pathways from a cutaneous melanoma tumor. For example, Uren et al 5 reported that in more than 10% of cases, lymphatic drainage from a cutaneous melanoma tumor went to three or more node groups in different anatomic regions. A tumor cell could migrate via any of those lymph channels, each of which leads to an independent sentinel lymph node (Fig 1). Current state of the art practice is to perform sentinel lymph-node staging for intermediate thickness (0.75 to 4.0 mm) cutaneous melanoma tumors. Other tumors for which staging using sentinel node histopathology has been performed include cancer of the penis, melanoma, breast cancer, cancer of the vulva, cancer of the uterine cervix, head and neck cancers, and cancer of the colon. For some genitourinary cancers, ileopelvic lymph drainage following perianal administrations of tracer have been reported. 8 Colorectal cancer has been investigated to identify sentinel lymph node(s) by injecting radiocolloid at the cancer site intraoperatively and using an intraoperative, hand-held gamma-detecting probe to find sentinel lymph node(s) to which the radiotracer has migrated via lymphatics. 9