Abstract: 【Abstract】 Objective To analyze the dermoscopic and reflectance confocal microscopic （RCM） features of extragenital lichen sclerosus, and to identify their associations with histopathological manifestations. Methods A total of 57 patients with histopathologically confirmed lichen sclerosus were retrospectively collected from the Department of Dermatology, Wuhan No.1 Hospital from October 2010 to April 2024. Dermoscopic and RCM images were collected from typical skin lesions in extragenital areas, and the consistency between dermoscopic or RCM characteristics and histopathological features was analyzed. Results Among the 57 patients with extragenital lichen sclerosus, there were 15 males and 42 females, with ages ranging from 5 to 60 years and disease duration from 5 to 28 months. The skin lesions were mainly located on the face and neck （23 cases, 40.4%） and back （11 cases, 19.3%）. Histopathological features included hyperkeratosis with follicular plugging, vacuolar degeneration of basal cells, edematous papillary and superficial dermis, collagen homogenization, and predominant infiltration of variable amounts of melanophages and lymphocytes in the superficial dermis. Dermoscopy showed yellowish-white structureless areas in 57 cases （100%）, yellowish-white circular structures in 55（corresponding to follicular keratotic plugs, 96.5%）, characteristic vascular structures in 54 （94.7%）, gray-brown punctate pigmentation in 56 （98.3%）, xanthochromic patchy pigmentation in 20 （35.1%）, white scales in 54 （94.7%）, white scar-like hypopigmentation in 43 （75.4%）, and hemorrhagic spots in 2 （3.5%）. RCM images showed follicular plugging in 44 cases （77.19%）, manifesting as dilated follicular infundibula containing highly refractive keratotic materials; liquefaction degeneration of the basal cell ring was observed in 57 cases （100%）, manifesting as loss of the basal cell ring, blurred epidermal-dermal junction, and infiltration of variable amounts of melanophages and inflammatory cells in the superficial dermis; dilatation of superficial dermal blood vessels was seen in 46 （80.7%）; all 57 cases （100%） showed reduced epidermal thickness compared to surrounding normal skin, epidermal atrophy and thinning, and rete ridge flattening; hyperkeratosis was observed in 57 cases （100%）; 39 cases （68.42%） showed thickened fibers with increased refractivity in the superficial dermis. The detection rates of follicular keratotic plugs, patchy pigmentation, and white scar-like hypopigmentation by dermoscopy significantly differed from those by histopathological examinations （all P < 0.05）, so did the detection rates of superficial dermal collagen thickening and vascular dilatation by RCM （both P < 0.05）. Conclusions Extragenital lichen sclerosus has characteristic dermoscopic and RCM manifestations, which were highly consistent with its histopathological findings. Dermoscopy combined with RCM technology can provide effective support for the diagnosis and differential diagnosis of extragenital lichen sclerosus.

Key words: Lichen sclerosus et atrophicus, Dermoscopy, Microscopy, confocal, Histology, comparative, Diagnosis, differential, Lichen sclerosus