This undated image provided by University of California, San Francisco shows a blood clot in the shape of a bronchial tree. University of California, San Francisco

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