Clinical and Histopathological Assessment of the Field of Cancerization in Human Skin Before and After Treatment With a 1927‐nm Thulium Fractional Laser

BACKGROUND: Field cancerization is a major concern in photodamaged skin due to its risk of progression to squamous cell carcinoma. The 1927-nm thulium laser has emerged as a promising therapy, but its isolated effects on this condition remain underexplored. OBJECTIVE: To evaluate clinical and histopathological changes in field cancerization treated with the 1927-nm thulium laser. METHODS: It was a prospective, observational, and interventional clinical study. Twenty-three patients (age average of 61.3 years), phototype I-III, with facial photodamage and multiple actinic keratosis underwent 4 monthly sessions of thulium laser, followed by a 3-month evaluation. Outcomes included lesion counts and a photoaging scale at each session, along with comprehensive histological analysis of pre- and post-treatment biopsies from 20 patients. RESULTS: There was a significant reduction in AK count (p < 0.001) and photoaging parameters (p < 0.001). Histologically, we observed improvement in vertical extension of keratinocyte atypia (p = 0.046), increased dermal thickness (p = 0.012), and fibroplasia (p < 0.001). No severe adverse effects occurred. CONCLUSION: The 1927-nm thulium laser is a safe, well-tolerated and has promising results as a field-directed therapy for actinic keratosis, promoting both clinical and histopathological improvement.