The goal of this prospective observational study is to evaluate the presence of circulating tumoral cells in patients over 18 with a stage I-III resectable Merkel cell carcinoma after the initial therapeutic sequence of surgery and radiotherapy. The main question it aims to answer is :
Can any residual disease be found in the form of circulating tumoral cells in blood samples of patients treated with surgery and radiotherapy for a resectable, stage I to III Merkel cell carcinoma ? When possible, the circulating tumoral cells count will be compared to the one realized in a blood sample of the same patient before surgery and radiotherapy.
Participants will :
* Have a blood sample taken before surgery (if the patient is addressed to our center early enough), * Have a blood sample taken immediately after surgery and radiotherapy (for all). * Two additional blood samples will be taken during the 6-months and 12-months visit to set up a biobank.
Patients at least 18 years old
Patients managed for stage I to III Merkel cell carcinoma,
For whom complete remission by complete surgical resection is planned (group B) or has been achieved recently, within 6 weeks prior to the inclusion visit (group A).
Pregnant or breast-feeding women
Failure to obtain written informed consent after a reflection period
Participant in another research study with an ongoing exclusion period
Not affiliated to a social security scheme