Abstract
RATIONALE: The World Health Organization defines a perivascular epithelioid cell tumor (PEComa) as a mesenchymal neoplasia composed of perivascular epithelioid cells with characteristic morphological and immunohistochemical features. Although PEComas have the potential to behave in a malignant fashion, malignant PEComas are extremely rare. PATIENT CONCERNS: An 83-year-old man visited our clinic presented with palpable, painless, and movable mass in the right knee area. DIAGNOSES: Malignant PEComa was diagnosed by incisional biopsy. No metastases was confirmed by radiologic imaging including PET/CT, magnetic resonance imaging, high resolution computed tomography. INTERVENTIONS: We performed wide excision of the mass and used an anterolateral thigh free flap to reconstruct the defect on the right knee. OUTCOMES: The permanent histopathology showed malignant PEComa was totally resected. The flap which was performed to cover the defect was survived and the patient discharge without any complications. LESSONS: PEComa can metastasize to various anatomical regions. Although there is no established standardized treatment, radical resection is still considered the cornerstone of treatment. Rapid and appropriate defect coverage is important to improve the patient's prognosis.