Abstract: Zeng Jingsi *, Zou Jun, Chen Guangbin, Xia Ying, Yang Zhen, Liu Houjun, Wang Chunsen, Yue Qing, Tu Yating, Huang Changzheng, Chen Siyuan. *Department of Dermatology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China Corresponding author: Chen Siyuan, Email: siyuanc_cn@126.com 【Abstract】 A 73-year-old male presented with mildly pruritic erythematous papules and plaques on the left leg for two years, which had developed into painful nodules and masses for half a year. Dermatological examination revealed multiple irregularly sized erythematous patches, plaques, nodules and masses on the distal one third of the extensor and fibular aspects of the left leg. The masses were hard, deeply infiltrating into the subcutaneous layer and ill-defined with tenderness and limited mobility. The skin covering the masses was partly normal. Histopathologically, there were focal aggregates of spindle cells and large cells of uneven size with red-stained cytoplasm and irregularly-shaped, heavily-stained huge nuclei in the mid and deep dermis as well as subcutaneous fat layer, with no obvious abnormality in the epidermis. Atypical mitoses were seen. There were light blue-stained substances admixed with lymphocytes in the Alcian blue-stained stroma. Immunohistochemistry revealed that the spindle cells and atypical large cells diffusely expressed vimentin. Of the tumor cells, 30% － 40% stained positive for Ki67, some for CD34 and CD68, while all stained negative for leukocyte common antigen, S100, pan cytokeratin, CD31, smooth muscle actin and desmin. A diagnosis of myxoinflammatory fibroblastic sarcoma was made.

Key words: Myxoinflammatory fibroblastic sarcoma, Rare diseases