ABSTRACT

The technique of cutaneous lymphoscintigraphy (LSG) includes a four-point intradermal injection of 0.5-1.0 mCi (18.7-37 MBq) of filtered technetium-99m-sulfur colloid (Tc-99m-SC). An external gamma camera images the isotope migration to the nodal basin in real time and then in static images at various time intervals. The goals of LSG include the identification of nodal basins at risk in patients with melanomas at sites of ambiguous lymphatic drainage (especially truncal and head and neck locations); defining the number and relative location of SLNs within the basin; and identifying SLNs at either interval (in-transit) sites between the primary injection site and the regional nodal basin (Figure 13.1), or, in the case of ectopic SLNs, in completely unpredicted locations (Figure 13.2).