Abstract: Li Weiwei, Wu Wenting, Zhang Hua, Jin Qiuzi, Zhang Qian, Zhang Chunlei Department of Dermatology, Peking University Third Hospital, Beijing 100191, China （Li WW, Wu WT, Jin QZ, Zhang Q, Zhang CL）; Research Center of Clinical Epidemiology, Peking University Third Hospital, Beijing 100191, China （Zhang H） Corresponding author: Zhang Chunlei, Email: zhangchunleius@163.com 【Abstract】 Objective To investigate the diagnostic value of rosette sign under a polarized dermoscope. Methods Lesions with rosette sign were selected from polarized dermoscopic image database of the Department of Dermatology of Peking University Third Hospital between September 2014 and March 2017. Then, histopathologically confirmed lesions were further chosen, and the correlations between the rosette sign and diseases were analyzed. These histopathologically confirmed lesions were divided into actinic keratosis（AK） group and non-AK group, and differences in clinical and dermoscopic features were analyzed between the 2 groups. Statistical analysis was carried out by nonparametric test for comparisons of the number of rosette sign between the AK group and non-AK group, as well as between different body sites. Results A total of 4 956 dermoscopic images of skin lesions were analyzed retrospectively, among which there were 144 （2.91%） skin lesions with rosette signs. Among the 144 skin lesions, 74 were histopathologically diagnosed, 37 （50.00%） of which were diagnosed as AK. Compared with the non-AK group, the AK group showed significantly higher proportions of lesions on the face （χ2 = 23.786, P < 0.001）and at sun-exposed sites （χ2 = 12.921, P < 0.001）, and prevalence of superficial scales （χ2 = 7.056, P = 0.008）, keratotic plugs （χ2 = 6.167, P = 0.013） and hair follicle openings surrounded by a white halo （χ2 = 4.893, P = 0.027） under a dermoscope. Moreover, the number of rosette sign was significantly higher in facial lesions than in non-facial lesions （Z = -2.581, P = 0.010）, as well as in lesions at exposed sites than in those at unexposed sites （Z = -2.098, P = 0.036）. Conclusions The rosette sign is mainly observed in AK lesions. If lesions on the face or at sun-exposed sites are characterized by rosette sign, and superficial scales, keratotic plugs and hair follicle openings surrounded by a white halo can be observed under a dermoscope, these lesions can be diagnosed as AK with a high probability.

Key words: Keratosis, actinic, Dermoscopy, Microscopy, polarization, Diagnosis, Rosette sign