This specimen shows a saccular aneurysm arising from the arch of the aorta, immediately beyond
the origin of the left subclavian artery. The aorta is not severely affected by atheroma; this fact and
the position of the aneurysm raise suspicion that it may be traumatic in origin. (However, the tear
in the intima that is associated with chest trauma usually occurs in the region of the attachment of
the ligament remaining after obliteration of the ductus arteriosus, which is on the opposing side of
the aorta). The aneurysm is occupied by blood clot.