There is an old Arab saying that goes something like this: "The enemy of my enemy is my friend." Here is a medical illustration of that sentiment.
Below are three slices from an abdominal CT of a patient with known lymphoma. The most recent examination showed much less disease, and a completely normal aorta. Today, however, the periaortic adenopathy has increased markedly. But....look at the aorta!
At this point, I'm not certain if there is a small dissection, a small leak forming a pseudoaneurysm, an ulceration, or even an infectious process involving the aorta. What I do know is that the huge node mass appears to be tamponading, or sealing, the abnormality in the aorta, and quite ironically is keeping the patient from bleeding out.
The patient was to go for surgical consult; I would expect he will undergo endografting rather than any sort of open procedure.
Wonders never cease in this business.