Clinicopathological significance of sentinel node biopsy in Japanese patients with cutaneous malignant melanoma

Sentinel node biopsy (SNB) for malignant melanoma began to be performed in our department in 1997. A total of 121 patients underwent SNB. Sentinel node (SN) were identified in 39 (83.0%) of the 47 cases in which the blue dye method alone was used, and in 71 (95.9%) of the 74 cases by combination of dye, radioisotope, and γ probe methods. The excised SN was cut through its longest meridian, and the cut surfaces were stained with hematoxylin and eosin (HE) and examined for the presence (SN⁺) or absence (SN⁻) of melanoma cells. If no melanoma cells were detected, serial sections were prepared and examined by sequential staining with HE, for S-100 protein, with HE, for HMB-45, with HE, and for Melan-A. In this study minute metastasis (SNm⁺) was defined as tumor cells newly identified in the immunostained section. The thickness of tumors ranged 0–38.0 mm, and their mean thickness was 4.5 mm. There were 39 SN⁺ cases (39/110 [39 + 71]; 35.5%) and seven SNm⁺ cases (7/110 [39 + 71]; 6.4%). The 5-year survival rate was significantly higher in the SN⁻ group than in the SN⁺ group and SNm⁺ group combined (P = 0.0002). The survival rate of the SNm⁺ group was not significantly different from that of the SN⁺ group (P = 0.3848). The 5-year survival rate of the SN⁺ group and SNm⁺ group combined was significantly higher than that of the group with clinically unequivocal metastatic nodes (P = 0.0001). Accurate SNB results will provide important prognostic information for Japanese patients with melanoma.