Dermoscopic features of actinic keratosis and follow up with dermoscopy: a pilot study.

Actinic keratosis (AK) is a common precursor of sun-related squamous cell carcinoma. AK is difficult to be differentiated from other malignancies with the naked eyes. Dermoscopic features of AK were previously described in some studies, but not extensively investigated. We investigated the dermoscopic features of AK in Asians and assessed dermoscopy as a post-treatment monitoring tool of AK. We retrospectively examined 34 AK lesions which had been diagnosed by histology. The changes of dermoscopic features and histopathological findings were assessed in all these lesions before and after treatment. Before treatment, 18 lesions were pigmented and 16 lesions were non-pigmented AK dermoscopically. The frequent dermoscopic features of AK were keratin/ scales (79.4%), red pseudonetwork (73.5%), targetoid-like appearance (55.9%), rosette sign (38.2%) and absent fissures/ridges, crypts and milia-like cysts. All the lesions had been treated with either photodynamic therapy, cryotherapy or 5% imiquimod cream. After treatment, dermoscopic features of 33 AK lesions were decreased or disappeared, and skin biopsies confirmed that atypical keratinocytes disappeared. One lesion showed accentuated and new dermoscopic features after treatment, and skin biopsy also showed progressing squamous cell carcinoma. In conclusion, scales, red pseudonetwork, targetoid-like appearance and rosette sign were common dermoscopic findings of AK in Asians. In most cases, the treatment response correlated with the changes in dermoscopic features. These findings suggest that dermoscopy is a useful tool to monitor AK.