Solar or actinic keratosis is a frequent pre-malignant lesion that often occurs in areas exposed to sunlight, and has a 6-10% relative risk of developing into squamous cell carcinoma. Patients with actinic keratosis have multiple and confluent subclinical lesions, leading to the characterization of the condition as being of the field cancerization type. They are multifocal areas with genetic mutations that may become the site of new primary tumors and local recurrence. In recent years, there has been increasing interest in the development of non-invasive diagnostic tests and treatment for these subclinical lesions, with an aim at preventing squamous cell carcinoma.

Keywords: KERATOSIS, ACTINIC; CARCINOMA, SQUAMOUS CELL; PHOTOTHERAPY.

INTRODUCTION: Actinic keratosis (AK) is a pre-malignant lesion that can progress to squamous cell carcinoma. The diagnosis is through clinical, dermatoscopic and confocal microscopy assessment. Currently, the approach is the treatment of the field cancerization, comprising of clinically visible and subclinical AKs, for which photodynamic therapy (PDT) is a therapeutic option.
OBJECTIVE: To evaluate improvement of AKs and cancerization field in patients submitted to daylight PDT, with clinical, dermatoscopic and confocal microscopy assessment.
METHODS: Ten patients with multiple AKs on the face were selected. Daylight PDT was performed using methyl aminolevulinate and clinical, dermatoscopic and confocal microscopy photographic documentation was performed before and 60 days after the treatment.
RESULTS: Of the nine patients who completed the treatment, 8 (88.8%) showed clinical improvement and reduction in the severity of AK with one treatment. On dermatoscopy, 4 patients (44.4%) showed significant improvement, 3 patients (33.3%) showed partial improvement and 2 patients (22.2%) had no change. On confocal microscopy, 6 (66.6%) patients presented reduction in the severity of the lesion.
CONCLUSIONS: Daylight PDT proved to be effective for the treatment of AKs, with high tolerability and efficacy, besides a good safety profile.

Keywords: Dermoscopy; Keratosis, Actinic; Microscopy, Confocal; Photochemotherapy