Regional Histological Differences of Actinic Keratoses Between Head and Body Sites

Background Actinic keratoses (AKs) are common in situ neoplasms and precursors of cutaneous squamous cell carcinoma. Regional histological severity and proliferation patterns are poorly defined. Objective The objective was to investigate differences of histologic grading between head and body lesions. Methods In total, 486 histologically confirmed AKs were retrospectively analysed and graded using the traditional AK I–III system and the basal proliferation grading (PRO I–III). Lesions were grouped by location (head, upper extremity, lower extremity and décolleté). Results Body lesions showed higher rates of AK III (40.0% vs. 26.0%) and PRO III (67.1% vs. 19.0%) than head lesions ( p < 0.0001). PRO III predominated on the décolleté (72.2%) and lower extremity (56.0%), whereas AK I and PRO I were more frequent on the head. These results parallel clinical observations that trunk and extremity AKs are more therapy‐resistant, with higher relapse rates than cephalic lesions. Consequently, AKs on the body, especially the décolleté and lower extremities, exhibit markedly greater histological severity and proliferative activity than their cranial counterparts. Conclusions Our findings highlight the need for region‐specific treatment strategies and stronger representation of body sites in future trials.