4 distinct biopsies will be taken

1. in a non UV-exposed area (inner arm)
2. in a UV-exposed area (external surface of the forearm)
3. in a pretumoral region (actinic keratosis)
4. inside the tumor

4 distinct biopsies will be taken

1. in a non UV-exposed area (inner arm)
2. in a UV-exposed area (external surface of the forearm)
3. in a pretumoral region (actinic keratosis)
4. inside the tumor

We will select the miRNAs differently expressed between biopsies obtained respectively from areas of normal, pretumoral and tumoral areas (candidate miRs = miRs potentially involved in tumor transformation of epidermal keratinocytes). This will be assessed by analyzing in each of the biopsies from each patient, the expression of different miRs that are known to date, using a dedicated microarray, then by checking the data obtained by quantitative PCR.