Frequency of pre‐existing actinic keratosis in cutaneous squamous cell carcinoma

Abstract

Background Controversy over the rate of malignant transformation of actinic keratosis (AK) into cutaneous squamous cell carcinoma (SCC) has generated considerable debate regarding the importance of treating all such precancers to preclude their transofrmation. Current changes in US healthcare policy will deny many individuals access to certain simple and effective treatment modalities for precancerous lesions. Objective Our purpose was to determine whether there is a significant association between the presence of cutaneous SCC and pre‐existing AK. Methods One hundred and sixty five consecutive cases of cutaneous SCC, retrieved from the files of a university‐affiliated dermatopathology laboratory serving north‐central Florida, were selected for review by a single dermatopathologist (D.M.). Hematoxylin and eosin stained skin tissue slides were examined under light microscopy for the presence of AK in close proximity to, or giving rise to, cutaneous SCC. Results Of the 165 cutaneous SCC cases reviewed, 82.4% (136 out of 165) were found to have concomitant AK giving rise to and/or in close proximity to SCC. Of the 136 AK‐positive SCC cases, 26.7% (44) were identified as superficial SCC arising within an AK (AKSSCC) and 55.7% (92) had AK in close proximity to SCC (AK + SCC). Close proximity is defined to include AK changes located directly adjacent to (on the shoulder of) SCC, to a maximum distance of 8 mm away. Conclusions The 82.4% prevalence of concomitant AK and cutaneous SCC in our biopsy population suggests a strong correlation between these two lesions. The fact that 26.7% of these lesions had SCC arising from AK highlights the importance of early recognition and effective treatment for AK.