• Be willing and able to provide written informed consent/assent for the trial.

• Be \>/= 18 years of age on day of signing informed consent.

• Present with a resectable head and neck mucosal melanoma.

• Be eligible for surgical treatment (without any contraindications).

• Be eligible for adjuvant radiotherapy.

• Have measurable disease based on RECIST 1.1.

• Be willing to provide tissue from a newly obtained core or excisional biopsy of a tumor lesion. Newly-obtained is defined as a specimen obtained up to 6 weeks (42 days) prior to initiation of treatment on Day 1. Subjects for whom newly-obtained samples cannot be provided (e.g. inaccessible or subject safety concern) may submit an archived specimen only upon agreement from the Sponsor.

• Have a performance status of 0 or 1 on the ECOG Performance Scale.

• Demonstrate adequate organ function as defined in table 1, all screening labs should be performed within 10 days of treatment initiation.

⁃ Female subject of childbearing potential should have a negative urine or serum pregnancy within 72 hours prior to receiving the first dose of study medication. If the urine test is positive or cannot be confirmed as negative, a serum pregnancy test will be required.

⁃ Female subjects of childbearing potential should be willing to use 2 methods of birth control or be surgically sterile, or abstain from heterosexual activity for the course of the study through 120 days after the last dose of study medication. Subjects of childbearing potential are those who have not been surgically sterilized or have not been free from menses for \> 1 year.

⁃ Male subjects should agree to use an adequate method of contraception starting with the first dose of study therapy through 120 days after the last dose of study therapy.

⁃ Patient affiliated to a social security system or beneficiary of the same

⁃ For the cohort B, patients must met the following additional criteria :

⁃ Not having any contraindication for lenvatinib treatment