Sentinel Node Biopsy for Melanoma Staging

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Summary and Comment

Sentinel Node Biopsy for Melanoma Staging

Prophylactic lymphadenectomy in patients with melanoma is controversial, because the associated morbidity may not justify the often minimal effect on survival. Studies have shown that prophylactic lymphadenectomy improves survival only in intermediate-thickness (1.5 to 3 mm) melanomas draining to one lymph node group. Lymphoscintigraphy is often used to determine the location of the draining lymphatic basin. In addition, sampling the sentinel nodes (the first nodes in a group to which tumor cells initially localize) reliably predicts the presence or absence of tumor in the other nodes in the group in 98.5% of patients. The sentinel nodes can be identified by injecting blue dye in the area of the tumor and dissecting out the lymph nodes that turn blue. However, considerable dissection is often required to locate the dye-stained nodes. These investigators aimed to improve on the blue-dye technique.

They injected a radioactive tracer, technetium-99, around the primary melanoma in 121 patients without clinically positive lymph nodes. The lymphatic drainage basins were identified with lymphoscintigraphy, and the sentinel lymph nodes were then localized with a handheld gamma probe. The sentinel nodes were successfully located and resected in 98% of patients, and localization of the nodes required less dissection than is usually needed for the blue-dye technique. Removal of all sentinel nodes was confirmed by a drop in gamma counts to baseline. In 3% of patients, the sentinel nodes were located outside of the expected lymphatic basins, and in 17% more than one drainage basin was identified.

Comment: Sentinel lymph node localization and resection combined with lymphoscintigraphy in patients with intermediate-thickness and thick melanomas offers several advantages over prophylactic lymphadenectomy. It reliably identifies the draining lymphatic basin(s) and sentinel nodes. Sentinel node biopsy is highly predictive of the status of the rest of the nodes in the lymphatic basin. Therapeutic lymph node dissection is carried out only if the sentinel node is positive for tumor; therefore, a majority of patients are spared a lymph node dissection. Staging of the melanoma is greatly enhanced, especially in cases where multiple lymphatic basins are involved, as often occurs with melanoma on the trunk. The procedure can be performed under local anesthesia in an outpatient setting, and is associated with minimal morbidity.

Prospective studies are needed to determine if sentinel node biopsy confers a survival advantage over clinical observation or routine prophylactic lymphadenectomy in patients with clinically negative lymph nodes.

— GJ Hruza

Published in Journal Watch Dermatology August 1, 1995