Therapies that target specific molecules markedly inhibit cancer growth in several malignancies, and provide valuable strategies for the treatment of advanced melanoma. In recent years, BRAF and KIT have become established therapeutic targets in melanoma patients showing activating mutations in these oncogenes. However, it is crucial that genetic mutations present in the melanoma lesions are identified if the investigators are to design tailormade therapies for individual patients. The tumour genotypes that determine the selection of molecular-targeted therapies are usually identified in primary tumours; however, primary tumours are not always representative of metastases. Circulating free DNA may be a source of valuable information because it can be obtained via routine blood sampling, it provides real-time information about a patient's current disease state, and it allows monitoring and molecular characterization before and after chemotherapy. The aim of the study is to determine the mutational status in circulating DNA in melanoma metastatic patients, with the Sequenom Mass Array, a next generation sequencing technology. Results obtained before and after treatment will be compared with the primary tumor genotype.