Background: Strong nuclear expression of TFE3 protein resulting from gene fusion has been reported in some neoplasms. TFE3 amplification has been proven to be a novel mechanism leading to increased protein level only in several cases of perivascular epithelioid cell tumor and renal cell carcinoma. Such rare genetic alteration might be associated with poor prognosis or aggressive course. Herein, we first reported a case of undifferentiated sarcoma with epithelioid features harboring TFE3 amplification. Case presentation: A 66-year-old woman with a history of chronic lymphocytic leukemia and chemotherapy presented with a 4 cm palpable nodule in the left lower leg. Magnetic resonance imaging revealed an oval juxtacortical lesion to the anterolateral left tibia. Microscopically, the large epithelioid cells with marked pleomorphism and the small round cells intermingled with each other in a diffuse sheet or a hemangiopericytoma-like vascular growth pattern. Myxoid stromal change was evident focally, imparting a hypocellular appearance. Atypical mitotic figures and lymph node metastasis were identified while tumor necrosis was absent. Immunohistochemically, the tumor was positive for vimentin, TFE3, CD68 and CD34. TFE3 gene amplification was identified by fluorescence in situ hybridization. Surgical resection was performed. The patient was alive without recurrence 8 month after surgery.Conclusions: The present case might represent a novel entity. Our report expands the scope of tumors carrying TFE3 amplification, and raises more attention to this rare genetic alteration and its association with potential aggressive behavior of the tumor.