*Note: This is the same patient as the one in the previous case (Histo).
The patient's disease is a very aggressive non-Hodgkin's lymphoma, but with chemotherapy, you induce a remission. Unfortunately, a decade later, the patient dies. He had dyspnea on exertion, impaired exercise capacity, orthopnea, paroxysmal nocturnal dyspnea, and peripheral edema. Autopsy shows the following:
You attribute this unfortunate death to this:
Challenge: What is that chemical?
First image shown under fair use, second image shown under GNU Free Documentation License.