Analysis of somatic mutations in tumors is currently indicated for daily practice in all metastatic melanoma. Actually, this research is limited to the mutation of three biomarkers validated by the l'Institut National du CAncer (INCA): BRAF, NRAS and CKIT. Moreover, in some cases it requires invasive biopsies.

In this context, molecular characterization of a tumor material flowing (circulating tumor DNA and / or circulating tumor cells) could afford to benefit patients in the best conditions of current targeted therapies and future.

The main objective of this study will be to define the diagnostic sensitivity of a panel of biomarker on the circulating tumor DNA from peripheral blood.

The secondary objectives of this study will be:

• Study the concordance between mutations in circulating tumor DNA and mutations in tumor tissue - Study the associations between mutational profiles and clinical and histological features of melanoma.
• Study the prognostic impact on survival of the identified genetic profile from the circulating tumor DNA

Inclusion Criteria:

• patient with melanoma confirmed histologically
• patient with metastatic melanoma (stage III unresectable or stage IV)
• patient consenting to participate to the study
• patient enrolled in the national healthcare insurance program
• patient older than 18 years

Exclusion Criteria:

- Metastatic tumor whose origin is doubtful (uncertain melanoma)