Reflectance Confocal Microscopy and Dermoscopy of Facial Pigmented and Non-Pigmented Actinic Keratosis Features before and after Photodynamic Therapy Treatment

Simple Summary Actinic keratosis (AK) is a very prevalent precancerous condition that can progress to an invasive form of squamous cell carcinoma. Photodynamic therapy (PDT) is a relatively new therapeutic method, and it has become widely used to treat skin cancer of non-melanoma type, particularly because of its good cosmetic outcome. New noninvasive imaging techniques, such as in vivo reflectance confocal microscopy (RCM) or (video)dermoscopy, can help practitioners make a diagnosis and assess the efficacy of the ongoing treatment. Nevertheless, there are no studies with in vivo RCM assessing the effect of PDT on characteristic features of different AK subtypes. Our objective was to evaluate the prevalence of specific (video)dermoscopy and RCM features of pigmented and classical subtypes of AK before and after photodynamic therapy (PDT) treatment. New noninvasive imaging techniques such as RCM and (video)dermoscopy can help practitioners better visualize the efficacy of the ongoing PDT treatment in either classical or pigmented AKs subtypes.Abstract Actinic keratosis (AK), due to its widespread prevalence, as well as the possibility of progression to an invasive form of squamous cell carcinoma, requires treatment regardless of the clinical stage. New imaging techniques, such as in vivo reflectance confocal microscopy (RCM), significantly increase the accuracy of diagnosis and allow noninvasive evaluation of the therapeutic efficacy of the ongoing treatment. Our objective was to evaluate the prevalence of specific (video)dermoscopy and RCM features of pigmented and classical subtypes of AK before and after photodynamic therapy (PDT) treatment. We included patients with facial grade II AKs (25 pigmented, 275 non-pigmented) were included in the study. Skin lesions were evaluated by (video)dermoscopy and RCM at the baseline and three months after PDT. In classic AK, the most frequent dermoscopic findings were fine wavy vessels (96%), scale (92%), microerosions (48%), and "strawberry" pattern (36%), while pigmented AK was characterized mostly by "rhomboidal pattern" (80%), scale (60%), white globules (48%), "jelly sign", and superficial pigmentation (40%). RCM's most characteristic classic AK findings were abnormal honeycomb pattern in the spinous layer, epidermal inflammatory infiltrate, and solar elastosis that were present in 96% of lesions. Pigmented AKs presented mostly with dark central areas of parakeratosis (72%), mottled pigmentation (72%), dermal inflammatory infiltrate (64%), solar elastosis (60%), and abnormal honeycomb pattern in the spinous layer (56%). Dermoscopically, PDT resulted in complete disappearance of the "rhomboidal pattern" in both classical and pigmented AKs, "starburst pattern" and "jelly sign" in classical AKs, and inner gray halo, "rosette sign" and central crust in pigmented AKs. Three months after one PDT session, RCM evaluation showed mostly solar elastosis in both classical and pigmented AK subtypes, epidermal inflammatory infiltrate in classical AKs, and dermal inflammatory infiltrate in pigmented AKs. New noninvasive imaging techniques such as RCM and (video)dermoscopy can help practitioners better visualize the efficacy of the ongoing PDT treatment in either classical or pigmented AK subtypes.