Abstract: Xue Yanning, Chen Hao, Si Haipeng, Liu Yan, Tan Cheng, Min Zhongsheng Department of Dermatology, Affiliated Hospital of Nanjing University of TCM, Nanjing210029, China （Xue YL, Liu Y, Tan C, Min ZS）; Department of Pathology, Institute of Dermatology, Chinese Academy of Medical Sciences and Peking Union Medical College, Nanjing 210042, China （Chen H）; Department of Pathology, Jiangsu Province Hospital of TCM, Nanjing 210029, China （Si HP） Corresponding author: Min Zhongsheng, Email: minzhsh@sina.com 【Abstract】 Objective To investigate clinical and histopathological manifestations of cutaneous plasmacytosis. Methods The clinical and histopathological data were collected from 7 cases of cutaneous plasmacytosis and analyzed retrospectively. Results Of the 7 patients, 2 were female, and 5 were male. The average age was 42.4 years, and the duration of disease ranged from 2 to 10 years. All the 7 patients presented with multiple slow progressive brown patches and plaques. No abnormality was observed in routine examinations of blood, urine and faeces, electrocardiogram and abdominal ultrasonography in the 7 patients. Three patients underwent serum IgG detection, and their serum levels of IgG were all higher than reference values. Two patients were subjected to cytological examination of bone marrow, which showed the percentage of plasma cells （mainly mature plasma cells） was up to 5%. Histopathological examination of 7 cases showed pigmentation in the basal layer of the epidermis, and infiltration mainly consisting of lymphocytes and mature plasma cells around the blood vessels in the dermis. Immunohistochemical study revealed that the ratio of κ to λ light chain was approximately 1∶1, and the plasma cells were strongly positive for IgG. IgG4 was positive in very few plasma cells in 1 case, and negative in the other 6 cases. Conclusion The etiology of cutaneous plasmacytosis is still unclear, but it has characteristic clinical and histopathological manifestations.