Abstract
Objective: To establish the relationship between tumor thickness (TT) and metastatic rate of the sentinel lymph nodes (SLN) in Japanese patients with melanoma. Methods: A retrospective review of 259 patients who underwent successful SLN mapping and biopsy in 13 facilities in Japan from April of 2003 to June of 2006. The data were analyzed with the χ2 or Fisherʼs tests. Result: The metastatic rate of SLN in each T-classification category was as follows: pTis: 0% (0/36), pT1: 11.3% (6/56), pT2: 21.0% (13/63), pT3: 34.0% (35/103), and pT4: 62.4% (63/101). Two of T1 cases with SLN metastasis were T1b, and the remaining 4 cases with SLN metastasis were T1a, in which TT was 1.0, 0.8, 0.55, and 0.50 mm. Metastatic rates of SLN in patients with primary lesions over 4 mm in thickness were as follows: 4.01–5 mm: 40.0%, 5.01–6 mm: 57.9%, 6.01–7 mm: 53.8%, 7.01–8 mm: 62.5%, 8.01–9 mm: 87.5%, 9.01–10 mm: 87.5%, and 10 mm<: 72.0%. The metastatic rates of SLN were significantly higher in cases with ulcerated primary lesions than in those without ulceration in T1–T4 and T1–T3 groups (p<0.001). Conclusion: In melanoma patients with thicker primary lesions, the indication for SLN biopsy should be decided taking into consideration the predictive metastatic rates and locations of SLN. Further study is needed to define criteria for performing SLN biopsy in patients with melanomas less than 1.0 mm thick.
