To investigate the value of dermoscopy in differential diagnosis of actinic keratosis (AK) .

Pathologically confirmed facial AK lesions were selected from the dermoscopic database of Peking University Third Hospital, and served as case group. At the same time, the facial lesions of other diseases were selected and served as control group, which were firstly suspected to be AK, but pathologically confirmed as other diseases. Dermoscopic features were compared between the two groups. Diagnostic test was used to evaluate the diagnostic value of dermoscopy for AK, based on the gold standard pathological examination.

There were 43 facial AK lesions in the case group and 22 facial lesions of other diseases in the control group. Eight dermoscopic features were observed more frequently in the case group than in the control group (all P < 0.05) , including a background erythema and red pseudonetwork (88.37%[38/43]vs. 36.36%[8/22]) , hair follicle openings surrounded by a white halo (90.70%[39/43] vs. 36.36%[8/22]) , hair follicle openings filled with yellowish keratotic plugs (95.35%[41/43]vs. 45.45% [10/22]) , white to yellow surface scales or keratin mass (97.67%[42/43]vs. 72.73%[16/22]) , rosette sign (60.47%[26/43]vs. 22.73%[5/22]) , large irregular linear vessels surrounding the hair follicles (44.19% [19/43]vs. 18.18%[4/22]) , fine, linear-wavy vessels surrounding the hair follicles (67.44%[29/43]vs. 36.36%[8/22]) and peripheral pigmentation (32.56%[14/43]vs. 4.55%[1/22]) . Among the above eight dermoscopic features, hair follicle openings surrounded by a white halo, a background erythema and red pseudonetwork, hair follicle openings filled with yellowish keratotic plugs and rosette sign showed higher Youden′s indices of 0.54, 0.52, 0.50 and 0.38 respectively, white to yellow surface scales or keratin mass showed the highest sensitivity of 97.67%, and peripheral pigmentation showed the highest specificity of 95.45%. The combination of 3 features (including a background erythema and red pseudonetwork, hair follicle openings surrounded by a white halo and follicular plugs) showed the highest diagnostic value, and the sensitivity, specificity, positive predictive value, negative predictive value and Youden′s index of the combination were 90.70%, 81.82%, 90.70%, 81.82% and 0.73, respectively, with the coincidence rate between dermoscopy and pathological diagnosis being 80.00%.

Facial AK shows character-istic dermoscopy patterns, and the combination of the 3 features (a background erythema and red pseudonetwork, hair follicle openings surrounded by a white halo and follicular plugs) shows the highest diagnostic value for AK.

Keratosis, actinic; Skin neoplasms; Dermoscopy; Diagnosis, differential