Oat cell carcinoma presenting as a pseudoaneurysm.

A man thought to have a dissecting aortic aneurysm was found to have an oat cell carcinoma encasing the thoracic aorta and great vessels. This is the first reported association of pseudoaneurysm with an oat cell carcinoma and is only the third case of a tumor presenting as a pseudoaneurysm. False-positive or false-negative results of aortography, echocardiography, and thoracic CT scanning point out the shortcomings of modern, sophisticated laboratory and radiographic procedures.