Primary aortic tumors are extremely rare. A 73-year-old woman presented with a 8 kg weight loss associated with abdominal pain. Physical examination was normal. Laboratory tests disclosed increased acute phase reactants. Thoracic and abdominal CT scan showed diffuse splenic and renal hypodense lesions with thrombotic feature of the thoracic aorta extending on 9 cm length. Transesophageal echocardiography showed a large and heterogeneous floating mass advocating a thrombus developed on atheroma. Because of the high risk of embolism the patient underwent surgical replacement of the thoracic aorta. Histopathology revealed an epithelioid angiosarcoma of the aorta. A primary tumor of the aorta should be suspected in the presence of an intra-aortic process presenting features of thrombosis.