Wieselthaler told the Atlantic that in this case, the patient had an infection that increased levels of a protein called fibrinogen, which helps blood clots form; and higher levels of fibrinogen could have helped the man's large clot to stay intact when it was coughed up.
The photo of the incredible clot was shared by the New England Journal of Medicine.
A 36-year-old man literally coughed up a piece of his lung after being hospitalized with heart problems at a hospital in California.
Despite the best efforts of intensive care staff at the University of California San Francisco Medical Center, the man died a week later.
"During an extreme bout of coughing, the patient spontaneously expectorated an intact cast of the right bronchial tree", the journal explained.
"A 36-year-old man was admitted to the ICU with an acute exacerbation of chronic heart failure".
After coughing up part of his lung, the patient was immediately intubated and doctors performed a bronchoscopy, which is a test that allows them to examine airways. Don't say we didn't warn you. "It's a curiosity you can't imagine-I mean, this is very, very, very rare".
When Wieselthaler and his team delicately spread out the clot, they discovered "that the architecture of the airways had been retained so perfectly that they were able to identify it as the right bronchial tree based exclusively on the number of branches and their alignment". After he was extubated two days later, he had no further signs of coughing up blood.
The man died from heart complications a week after coughing up the clot.
In 2005, a heavily pregnant woman coughed up a similar but smaller bronchial tree clot.