Tyrosinase expression in the peripheral blood of stage III melanoma patients is associated with a poor prognosis: a clinical follow-up study of 110 patients

The aim of this study is to define the relationship between the tyrosinase expression in the peripheral blood and the clinical course of the disease in stage III disease-free melanoma patients after radical lymph node dissection. RT–PCR techniques were used to identify tyrosinase mRNA in 110 patients; a total of 542 blood samples were investigated. In all, 54 patients (49%) showed at least one positive result; 13 patients (11.8%) showed baseline positive results: six became negative thereafter, whereas seven showed follow-up positive results until disease progression occurred. One or more positive determinations were found during follow-up in 41 patients with negative baseline tyrosinase. No correlation was found between baseline results and the relapse rate or disease-free survival (DFS), whereas a significant correlation was found between positive tyrosinase results and disease recurrence during follow-up. In fact, 72.9% of positive patients relapsed, but only 19.3% of negative cases did so. The median interval between the positive results and the clinical demonstration of the relapse was 1.9 months (range 1–6.6). Disease-free survival multivariate analysis selected, as independent variables, Breslow thickness (P=0.05), lymph node involvement according to the AJCC classification (P=0.05) and tyrosinase expression (P=0.0001). In conclusion, RT–PCR tyrosinase mRNA expression is a reliable and reproducible marker associated with a high risk of melanoma progression and we encourage its clinical use in routine follow-up.