A 39-year-old man was referred to the Department of Oral and Maxillofacial Surgery at the Graduate School of Tokyo Medical and Dental University Hospital, Tokyo, Japan. He had begun to have painless swelling of the left side of the maxilla 3 months earlier, and the swelling had recently grown noticeably larger. The facial configuration was symmetric on clinical examination, but an intraoral examination showed a hard, well-defined, elastic swelling with a smooth surface on the hard palate. The lesion measured 38 35 20 mm (Fig 1). Contrast-enhanced computed tomography (CT) depicted a mass lesion of 35 mm in diameter expanding to the left sinus. The lesion manifested as an irregular slight enhancement. No metastatic images were observed in the head, neck, or lung. Contrast-enhanced magnetic resonance imaging showed an indistinctly bordered lesion measuring 41 31 28 mm extending from the left maxillary alveolar process in the left palate. This lesion showed intermediate signal intensity on the T1-weighted image and homogeneous high signal intensity on the T2-weighted image (Fig 2). During the patient’s first visit, our clinical impression was suspected salivary tumor of the left maxilla. One week fter the first visit, a small biopsy specimen was collected rom the left hard palatal swelling. Then, at 2 weeks after he first visit, the lesion was preliminarily diagnosed as a uspected synovial sarcoma or undifferentiated carcinoma f the left maxilla based on the first interim biopsy report. About 4 weeks after the first visit, evidence of rapid umor growth prompted us to initiate urgent treatment of he suspected sarcoma. The patient was hospitalized and cheduled for a therapeutic operation. Chemotherapy was dministered for 3 weeks (5-fluorouracil, 250 mg/fr, 5 fr/w, 4,100 mg) after cannulation of the left superficial temporal rtery for delivering 5-fluorouracil through the artery into