Risk factors for lymph node metastasis in cutaneous squamous cell carcinoma: a long-term retrospective study of Japanese patients.

BACKGROUND: Cutaneous squamous cell carcinoma (CSCC) is one of the most common skin cancers. Prognosis is favorable following surgical resection of early-stage disease, but the management of the metastatic disease is challenging. Several prognostic risk factors have been described in the American Joint Committee on Cancer/the Union for International Cancer Control (UICC) 8th edition staging and the Brigham and Women's Hospital T classification system. However, their clinical validity in Asian populations is unclear because of racial differences in the clinical characteristics of CSCC. This study aimed to identify factors that could predict lymph node metastasis in Asian patients.

METHODS: This retrospective single-center study evaluated 540 patients with primary CSCC between 1989 and 2013. Five factors were evaluated for their ability to predict lymph node metastasis: maximum tumor diameter, tumor thickness, depth of invasion, degree of differentiation, and infiltrative growth pattern (INF).

RESULTS: Tumor diameter > 2 cm (p < 0.0001), tumor thickness > 6 mm (p < 0.0001), invasion beyond the subcutaneous fat (p < 0.0001), poor differentiation (p = 0.042), and INFc infiltration (p < 0.0001) were associated with lymph node metastasis in the univariate analyses. In the multivariate analysis, lymph node metastasis was independently associated with tumor size > 2 cm [hazard ratio (HR) 2.9, 95% confidence interval (CI) 1.4-6.2; p = 0.006], tumor thickness > 6.0 mm (HR 2.9, 95% CI 1.3-6.4; p = 0.007), and invasion beyond the subcutaneous fat (HR 2.3, 95% CI 1.0-5.1; p = 0.045).

CONCLUSION: Larger tumor diameter, greater tumor thickness, and deeper invasion included in the UICC T classification system are associated with increased risks of lymph node metastasis from CSCC in Japanese patients.