Abstract: A 69-year-old female presented with red plaques and nodules with pruritus and pain on the left thigh for 2 years. The clinical manifestations were multiple red plaques and nodules of different sizes, with hard texture, deep base, unclear boundary with surrounding tissues, fusion and tenderness, ,and about 8.5 cm×11.0 cm in size. Pathology showed a subcutaneous spindle cell tumor with atypical nuclei, focal pathological mitotic figures, and numerous lymphoplasmacytic infiltrates, with interstitial mucinous degeneration. Immunohistochemical staining: Vimentin(+), CD68 (mostly+)and SMA(+); Ki-67 index (75%). The diagnosis of myxoinflammatory fibroblastic sarcoma was made.

Key words: myxoinflammatory fibroblastic sarcoma, soft tissue neoplasms, rare disease