Dermoscopy and methyl aminolevulinate: A study for detection and evaluation of field cancerization

Actinic keratosis (AK) is a keratinocyte intraepidermal neoplasia UV light-induced that frequently appears in sun-exposed areas of the skin. Although historically AK was defined as "precancerous", actually it is considered as the earliest stage of squamous cell carcinoma (SCC) in situ. Since AKs can progress into invasive SCC, their treatment is recommended. AKs rarely develop as a single lesion; usually multiple lesions commonly affect an entire area of chronically actinic damaged skin. This has led to the concept of "field cancerization", an area chronically sun-exposed that surrounds peripherally visible lesions, in which are individualized subclinical alterations. One of the main principles endpoint in the management of AKs is the evaluation and the treatment of field cancerization. In this view, in order to detect and quantify field cancerization, we employed a method based on the topical application of methyl aminolevulinate (MAL) and the detection of the fluorescence emitted by its metabolite Protoporphyrin IX (PpIX); then, considering the extension and the intensity of measured fluorescence, we create a score of field cancerization. The results show that patients underwent to daylight PDT had a reduction of total score, from T0 to T2. Whereas in the group untreated we observed a stability of total score or a slightly worse. So, the method and the score used allows to evaluate with a good approximation the dimension of field cancerization and show the modification of it after treatment.