Primary sarcomas of the great vessels are extremely uncommon tumors, with aortic sarcoma being the rarest type. They tend to occur in the thoracic aorta, followed by the abdominal aorta and the thoracoabdominal aorta. They have a propensity for metastases and they cause acute arterial embolism (1).Undifferentiated pleomorphic sarcoma, also called malignant fibrous histiocytoma, has been defined as a group of pleomorphic, high-grade sarcomas that fail to show any line of differentiation using currently available ancillary techniques (2). To the best of our knowledge, no fewer than 24 cases of undifferentiated pleomorphic sarcoma originating from the aorta have been reported in the worldwide literature, but imaging findings have been rarely reported (3-7).Herein, we describe the case of a 67-year-old male who had a primary undifferentiated pleomorphic sarcoma of the descending thoracic aorta with an emphasis on computed tomography (CT) and magnetic resonance imaging (MRI) findings. CASE REPORTA 67-year-old Russian male presented with a 5-month history of epigastric and back pain. The patient had a history of diabetes mellitus and hypertension. Laboratory studies revealed abnormal liver function test (gamma-glutamyl transpeptidase:143 IU/L, alkaline phosphatase: 448 IU/L) and increased C-reactive protein (1.98 mg/dL). Electrocardiogram showed normal sinus rhythm. Contrast enhanced abdomen and chest CT (64-slice multidetector CT, GE Healthcare, LightSpeed VCT, Milwaukee, WI, USA) were performed. Abdomen CT showed no significant findings, and contrast-enhanced CT of the patient's chest showed a heterogeneously enhancing lobulated mass encasing the right aspect of the descending thoracic aorta, extending from the T6 to T8 level, and measuring 1.8 × 3.5 × 3.2 cm in size (Fig. 1A, B). The mass occupied 20% of the aortic lumen, and the intimal layer of the aorta was intact. Thoracic Undifferentiated pleomorphic sarcoma, known as malignant fibrous histiocytoma, arising from the wall of the aorta is an extremely rare tumor. We report computed tomography and magnetic resonance imaging findings of a 67-year-old male patient with histopathologically proven undifferentiated pleomorphic sarcoma arising from the wall of the descending thoracic aorta. To the best of our knowledge, this is the first report of such a case in Korea. Knowledge of imaging findings of undifferentiated pleomorphic sarcoma will be helpful for accurate diagnosis and appropriate management.

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