Melanoma sentinel lymph node biopsy in the modern era.

The initial route of metastasis for many cancers, including melanoma, is via regional lymphatic channels. This fact, recognized more than a century ago, has spurred tremendous interest in the optimal method of assessing and treating lymph nodes and eventually led to the development of lymphatic mapping and sentinel lymph node (SLN) biopsy. The potential utility of nodal treatment includes providing the most accurate staging or prognostic information and removing early metastases in order to halt the cascade of metastatic spread in an effort to save the patient's life. In the past, pathologic assessment of regional lymph nodes required removal of all regional nodes, a procedure that results in moderate levels of short and long-term morbidity. SLN biopsy allows not only a minimally invasive method of nodal assessment, but one more accurate than full node dissection as it permits more intensive pathologic scrutiny of the tissue. The question of the therapeutic effect of SLN biopsy has been a subject of much controversy. There is clear evidence that SLN biopsy improves relapse-free survival in melanoma, but its effect on melanoma-specific and overall survival remains less clear.