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 gamma 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.