Systemic lymphoma that involves the aorta is called periaortic lymphoma, and may be misdiagnosed clinically or in CT sean, mimicking a thoracic aortic aneurysm, dissection, penetrating ulcer or an intramural hematoma. We report a 70 year-old woman in whom a systemic non-Hodgkin 's lymphoma ivas diagnosed after she presented with the clinical features of an acute aortic syndrome. A CT sean showed the presence of a large thoracoabdominal periaortic soft tissue mass without aneurism or dissection. Later, a biopsy of the mass ivasperformed which showed a non-Hodgkin's lymphoma. Chemotherapy with CHOP-R was effective, with complete initial resolution of the mass, developing in the follow up chylothorax, malnutrition and death.