Thick cutaneous malignant melanoma: a reappraisal of prognostic factors

The prognosis of patients with thick (>3 mm) cutaneous malignant melanomas is generally poor; however, some cases survive far longer than expected. Thus tumour thickness cannot serve as the only predictor of disease course in the individual patient. The aims of the current study were to evaluate the clinical outcome of patients with thick (>3 mm) cutaneous melanoma and test the prognostic value of a series of clinicopathological parameters on disease-free and cause-specific survival. We retrospectively evaluated 140 patients with stage I cutaneous melanoma >3 mm in thickness. Disease-free and cause-specific survival rates (Kaplan-Meier method) were compared using the log rank test. A multivariate analysis (Cox proportional hazards model) was used to determine the independent effect of each variable on prognosis. The overall 5-year and 10-year disease-free survival rates were 35.5% and 29.3%, respectively, whereas the overall 5-year and 10-year cause-specific survival rates were 55.3% and 47.7%, respectively. In the univariate analysis, the following factors were found to be significantly associated with the disease-free and cause-specific survival: tumour thickness, mitotic rate/mm2, type of invasive front, ulceration, thickness of the nodular component and predominant cell type. In addition, the presence of vascular invasion was significantly correlated with the risk of metastases but not with survival. In the multivariate analysis (Cox proportional hazards model), only tumour thickness (both as a continuous variable and >7.5 mm), infiltrating invasive front, presence of ulceration and mitotic rate/mm2 (both as a continuous variable and >10 mitoses/mm2) were significant independent predictors of poorer clinical outcome.