SAN FRANCISCO — Doctors at UC San Francisco Medical Center see a lot of things, but even they were stunned by this. They were treating a 36-year-old man with end-stage heart failure when he began coughing so violently, that he coughed up a 6-inch-wide blood clot from his lungs in the near-perfect shape of his right bronchial tree. The bright mass that looks like coral is a blood clot. The doctors were shocked, calling what happened extremely rare. Despite doctors’ best efforts, the man passed away a few days later. The information in this article was provided by the New England Journal of Medicine.