The early MR imaging characteristics of a malignant fibrous histiocytoma (MFH) in a 25-year-old man under the radiation treatment of nasopharyngeal carcinoma were presented in this study. The tumor developed four years and 9 months following the 3-dimentional conformal radiotherapy of nasopharyngeal carcinoma. Early magnetic resonance imaging features were nonspecific for neoplasm and not distinguishable from mycetoma. Final diagnosis of MFH was achieved based on histopathology and immunohistochemical stains. The patient underwent lateral rhinotomy and medial maxillectomy with the en bloc resection of the tumor with an uneventful postoperative course.