The main objective of this project is to perform a longitudinal monitoring of BRAF and NRAS cell-free DNA in a large cohort of metastatic melanomas patients before treatment and during the follow-up. Results will be compared with clinical data as imaging (based on RECIST criteria) and the activity of lactate dehydrogenase in serum (LDH).

During a consultation of follow-up for an advanced malignant melanoma (stage IIIb or IIIC or IV), an investigator presents the study to the patient and give him the note of information and the informed consent.

The patient can benefit from a reflexion period of of 7 days.

In case of agreement, a first blood draw will take place before initiation of any treatment. Between D15 and D30 a second blood draw will be taken. Then a blood draw will be necessary every two months until recurrence or progression of the disease for a maximum of 22 months.

Inclusion Criteria:

• Patients in metastatic situation for a malignant melanoma inoperable stage IIIB or IIIC or stage IV
• In first line of treatment by a targeted therapy (only or in association) or immunotherapy
• Every histological types of cutaneous or mucous malignant melanoma (excepted choroid melanomas)
• The tumor must be mutates for BRAF or NRAS
• The mutation status must have been realized in the Laboratory Pathology Clinical and Experimental (LPCE) of the CHU de Nice analysis of the status on-site metastatic mutational and/or primitive tumor must
• Membership or beneficiary of the national insurance scheme

Exclusion Criteria:

• Histories of cancer or other synchronous cancer
• Pregnant, breast-feeding Women. A pregnancy test will be practiced to the women old enough to procreate.
• Vulnerable People: adults under guardianship, patients deprived of freedom, minor