Background: The technique of sentinel lymph node (SLN) biopsy for melanoma provides accurate staging information because the histology of the SLN reflects the histology of the entire basin, particularly when the SLN is negative.
Methods: We combined two mapping techniques, one using vital blue dye and the other using radiolymphoscintigraphy with a hand-held gamma Neoprobe, to identify the SLN in 600 consecutive patients with stage I-II melanoma. The SLNs were examined using conventional histopathology and immunohistochemistry for S-100.
Results: Eighty-three (13.9%) patients had micrometastatic disease in the SLNs. Thirty percent of patients with primary melanomas greater than 4.0 mm in thickness had positive SLNs, followed by 48 of 267 (18%) of patients with tumors between 1.5 mm and 4 mm, and 12 of 169 (7%) of those with lesions between 1.0 mm and 1.5 mm. No patient with a tumor less than 0.76 mm in thickness had a positive SLN. Sixty-four of the 83 SLN-positive patients consented to undergo complete lymph node dissection (CLND), and five of 64 (7.8%) of the CLNDs were positive. All patients with positive CLNDs had tumor thicknesses greater than 3.0 mm.
Conclusions: The rate of SLN-positive patients increases with increasing thickness of the melanoma. SLN-positive patients with primary lesions less than 1.5 mm in thickness may have disease confined to the SLN, thus rendering higher-level nodes free of disease, and may not require a CLND.