FDG PET/CT Demonstrates Malignant Fibrous Histiocytoma in a Patient with Nasopharyngeal Carcinoma after Radiation Therapy

A 25-year-old young male is a victim of undifferentiated nasopharyngeal carcinoma (NPC) s/p an 8,200 cGy external radiation therapy about 5 years ago, who was referred to our positron emission tomography (PET) center for evaluating a protruding mass in his nasal cavity. 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) imaging incidentally demonstrated a hypermetabolic lesion in the right nasal cavity and right maxillary sinus, which was suggestive of tumor recurrence. However, the surgical pathology report showed a picture of moderately differentiated sarcoma characterized by bizarre tumor giant cells, abnormal mitotic figure and intermixed with inflammatory cells. The immunohistochemical stains of the tumor cells showed positive for vimentin, which was compatible with malignant fibrous histiocytoma (MHF). Since radiation therapy is a well-known risk factor of MFH, which remind us that MFH should be ruled out in a NPC patient post radiotherapy and PET/CT scan is a valuable modality in detecting a second cancer, such as MFH. Furthermore, MFH usually happen to aged subgroup at limbs and retroperitoneum, our report presented rare case of a young male with MFH involving maxillary sinus and nasal cavity.