The role of sentinel lymph node biopsy for melanoma

Regional lymph nodes are a common site of melanoma metastases, and the presence or absence of melanoma in regional lymph nodes is the single most important prognostic factor for predicting survival. Furthermore, identification of metastatic melanoma in lymph nodes and excision of these nodes may enhance survival in a subgroup of patients whose melanoma has metastasized only to their regional lymph nodes and not to distant sites. Sentinel lymph node (SLN) biopsy was developed as a low morbidity technique to stage the lymphatic basin without the potential morbidity of lymphedema and nerve injury. The presence or absence of metastatic melanoma in the SLN accurately predicts the presence or absence of metastatic melanoma in that lymph node basin. When performed by experienced centers, the false-negative rate of SLN biopsy is very low. As such, the nodal basin that contains a negative SLN will usually be free of microscopic disease. Since occult micrometastatic disease affects only 12% to 15% of patients with melanoma, selective SLN dissection allows up to 85% of patients with melanoma to be spared a formal lymph node dissection, thus avoiding the complications usually associated with that procedure. While standard pathologic evaluation of lymph nodes may miss metastatic melanoma cells, more sensitive techniques are developing which may identify micrometastases more accurately. The clinical significance of these micrometastases remains unknown and is the subject of active investigations.