Single-dose isotope injection for both preoperative lymphoscintigraphy and intraoperative sentinel lymph node identification in melanoma patients

For patients with melanoma the `sentinel' lymph node biopsy technique, although simple in concept, has the potential to provide misleading information if great care is not taken to ensure accurate sentinel node (SN) identification. The method initially reported involved lymphatic mapping by injection of blue dye around the primary melanoma site. Preoperative lymphoscintigraphy was subsequently shown to improve both the speed and accuracy of SN identification. More recently, intraoperative use of a handheld gamma probe has been recommended, and it is likely that maximum reliability of SN biopsy will be achieved if all three manoeuvres are undertaken. As originally described, use of a gamma probe intraoperatively followed injection of tracer a short time before the surgical procedure. We report a simpler method of confirming SN identity with a gamma probe, using residual activity in the node following lymphoscintigraphy the previous day. In 21 patients close concordance with preoperative lymphoscintigram results and intraoperative findings after blue dye injection confirmed the reliability of the technique. Avoiding the need for repeat isotope administration on the day of surgery simplifies logistics, reduces costs, minimizes inconvenience and radiation dose for patients, and eliminates potential health and safety problems for operating theatre staff.