Abstract: Zhang Dezhi, Pu Xiongming, Yu Shirong, Ding Yuan, Kang Xiaojing Department of Dermatology and Venereology, People′s Hospital of Xinjiang Uygur Autonomous Region, Urumqi 830001, China Corresponding authors: Pu Xiongming, Email: puxiongming@126.com; Kang Xiaojing, Email: drkangxj666@163.com 【Abstract】 Objective To investigate clinical manifestations, morphological characteristics of skin lesions, and histopathological features of cutaneous Rosai-Dorfman disease （CRDD）. Methods Basic information and clinical data were collected from 20 patients with CRDD. According to the morphological characteristics, the skin lesions were classified into different types, and then subjected to histopathological examination and immunohistochemical staining. Results Of the 20 patients with CRDD, 11 had multiple lesions, and 9 had solitary lesions. Skin lesions involved single anatomical site in 16 patients, multiple anatomical sites in 4 patients, and there were a total of 24 involved anatomical sites. Skin lesions on the 24 sites were divided into 3 main types, including papulonodular type （10/24, 41.67%）, infiltrating plaque type （12/24, 50.00%） and tumor-like type （2/24, 8.33%）. Of the 20 patients, 6 had mixed-type skin lesions, including 5 with papulonodular-type lesions complicated by infiltrating plaque-type lesions, and 1 with infiltrating plaque-type lesions complicated by tumor-like lesions. There were similar histopathological manifestations of skin lesions among the 24 involved anatomical sites. Concretely speaking, varying numbers of large histiocytes were scattered or distributed in sheets in the dermis and/or subcutaneous adipose tissue, with infiltration of plenty of inflammatory cells, mainly lymphocytes and plasma cells. Moreover, varying numbers of lymphocytes and neutrophils were observed in the cytoplasm of histiocytes. Immunohistochemically, these histiocytes were stained positive for S100 and CD68, but negative for CD1a. At 17 anatomical sites, lesions affected the full-thickness dermis, and the subcutaneous adipose tissues were involved at 13 of 17 sites. Of the 24 involved anatomical sites, lesions only affected the superficial to middle dermis at 6 sites, and affected the deep dermis and subcutaneous adipose tissue at 1 site. There were no obvious differences in the extent of lesion involvement and pattern of inflammatory infiltration among different morphological types of skin lesions. Conclusions CRDD mainly manifests as papulonodular-type and infiltrating plaque-type lesions, and tumor-like lesions are rare. Histopathologically, varying numbers of emperipoletic histiocytes can be observed in lesions of different types.

Key words: Histiocytosis, sinus, Histiocytes, Diagnosis, differential, Histopathology