Abstract: Wang Shiqi, Liu Jie, Liu Zhaorui, Chi Cheng, Liu Yuehua, Jin Hongzhong Department of Dermatology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, China Corresponding author: Liu Jie, Email:Liujie04672@pumch.cn 【Abstract】 Objective To describe high-frequency skin ultrasonographic and dermoscopic features of seborrheic keratosis （SK）. Methods Between August and December in 2017, 46 outpatients with SK were enrolled from the Department of Dermatology of Peking Union Medical College Hospital, and 50 SK lesions were observed by 50- and 20-MHz high-frequency skin ultrasonography and dermoscopy. The high-frequency ultrasonographic and dermoscopic features of SK lesions were summarized and analyzed. Statistical analysis was done by using chi-square test for comparisons of evaluation results of SK lesions between 50- and 20-MHz ultrasonography, and the correspondence between high-frequency skin ultrasonographic and dermoscopic features of SK was analyzed by calculating the simple matching coefficient. Results As 50- and 20-MHz ultrasonography showed, ultrasonographic features of SK lesions from top to bottom were enhanced hyperecho （48/50 vs. 39/50, respectively, P = 0.007）, enhanced hyperechoic masses or spots in the stratum corneum （22/50 vs. 11/50, respectively, P = 0.019）, sound shadows behind the epidermis （34/50 vs. 13/50, respectively, P < 0.001）, skin lesions with regular shapes and clear borders （46/50 vs. 41/50, respectively, P = 0.137）, heterogeneous hypoechoic areas in the lesions （50/50 vs. 47/50, respectively, P = 0.079） and internal hyperechoic spots （25/50 vs. 2/50, respectively, P < 0.001）, the lesional bottom being at the same level （40/50 vs. 36/50, respectively, P = 0.349）, and reduced dermal echogenicity below the lesion （50/50 vs. 28/50, respectively, P < 0.001）. In regard to the overall evaluation of the above 8 ultrasonographic characteristics, 50-MHz ultrasonography was superior to 20-MHz ultrasonography （P = 0.002）. The common dermoscopic features of the 50 SK lesions were clear borders （n = 50）, comedo-like openings （n = 45）, ridge or cerebriform pattern （n = 31）, hairpin-like vessels （n = 30）, multiple milia-like cysts （n = 24）, moth-eaten border （n = 21） and shiny white streaks （n = 3）. Under 50- and 20-MHz ultrasonography, the simple matching coefficients between enhanced hyperechoic masses or spots in the stratum corneum and comedo-like openings under dermoscopy were 42% （21） and 20% （10） respectively, and the simple matching coefficients between internal hyperechoic spots and multiple milia-like cysts （> 3） under dermoscopy were 58% （29） and 48% （24） respectively. Conclusion High-frequency skin ultrasonography and dermoscopy both are of great value to the assessment of SK lesions, and 50-MHz ultrasonography is superior to 20-MHz ultrasonography for imaging skin lesions.

Key words: Keratosis, seborrheic, Ultrasonography, Dermoscopy, Pathologic processes, Skin manifestations