A sentinel lymph node (SLN) is the first lymph node or group of nodes to receive lymphatic drainage from a tumor at a particular anatomic area. Thus, an SLN is most likely to contain any metastatic deposits.
Within the past 15 years, evaluation of SLNs has become the most popular method for early staging of several malignancies, including breast carcinoma, gastrointestinal carcinoma, and melanoma. The main advantages SLN biopsy has over complete lymphadenectomy are: (1) the lower number and lesser degree of side effects and (2) the selection of a small number of lymph nodes that can then be extensively analyzed by the pathologist (through examination of hematoxylin and eosin [H&E] sections and immunohistochemistry [IHC]).
Approximately 20% of patients with primary cutaneous melanoma will have metastatic melanoma in their SLN. According to most published data, patients in whom the SLN contains metastatic melanoma have a poorer prognosis. These patients are then offered a completion lymphadenectomy to remove the remainder of the lymph nodes in that anatomic area. Current studies are analyzing the possible therapeutic effect of removing positive SLNs.
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