The reproducibility in routine clinical practice of sentinel lymph node identification by pre-operative lymphoscintigraphy in patients with cutaneous melanoma.

Pre-operative lymphoscintigraphy (LS) is an important part of successful sentinel lymph node (SLN) biopsy in most melanoma treatment centers. The test accurately maps lymphatic drainage from cutaneous melanoma sites and has been shown to be reproducible in prospective studies. Its reproducibility has not been tested, however, in routine clinical practice. Occasionally, after LS has been performed to map the location of SLNs, the patient is unable to proceed to SLN biopsy surgery within the time limit imposed by the radioactive decay of the 99mTc label attached to the colloid particles. In this situation, the surgery is rescheduled and LS repeated to relabel the SLNs so that they may be accurately biopsied. This has happened on 21 occasions at the Sydney Melanoma Unit and we have performed a retrospective analysis of the reproducibility of the LS results. In 19 patients, the same SLNs were shown in the same locations on the two studies. Two patients had discrepant results. One showed two extra interval nodes on the back as well as concordant flow to SLNs in each axilla. The other with a leg melanoma showed the same groin SLNs but failed to relabel the two popliteal SLNs on the second study. SLN locations were identical during 95%, and SLNs were identical 94% of the time. These results indicate that in routine clinical practice LS is a highly reproducible procedure to locate and radiolabel the SLNs prior to biopsy in patients with melanoma.