While doctors still aren't 100 per cent sure how the clot stayed completely intact on its way up the man's throat, Dr Wieselthaler suspected it was because the man had more fibrinogen in his blood.
Earlier this week the New England Journal of Medicine tweeted a photo of what looked like a lovely piece of bright red coral to their 545,000 followers.
It came from a 36-year-old man with end-stage heart failure who spat out the medical anomaly in one piece during a coughing fit in hospital.
The patient reportedly had a medical history including "heart failure with an ejection fraction of 20 per cent, bioprosthetic aortic-valve replacement for bicuspid aortic stenosis, endovascular stenting of an aortic aneurysm, and placement of a permanent pacemaker for complete heart block". Last week, a hospitalized California man coughed up an intact cast of part of his right lung, a colossal blood clot almost six inches wide.
A 36-year-old man was admitted to the ICU with an acute exacerbation of chronic #heartfailure.
The University of California at San Francisco transplant and pulmonary surgeon Georg Wieselthaler said he and his team were "astonished" when they saw the bronchial tree-shaped blood clot. Don't say we didn't warn you. "It's a curiosity you can't imagine-I mean, this is very, very, very rare", he said in a The Atlantic report.
Though it resembles a coral, root system, or some other kind of growth, the above photo actually depicts a blood clot over 15cm wide in the near-perfect form of the right bronchial tree of a human lung, the Atlantic reported on Thursday.
The bronchial tree is made up of the trachea and the two primary bronchi, which are the tubes that distribute air to the lungs.
Despite the doctor's best efforts and the assistance of a ventrical device, the man died from heart failure a week later.