This question came up at lunch today, and I didn't believe my friend when he said someone had a pine tree growing in his lungs.
I have found several sources: 1, 2, 3
Source #2 has a key note:
There was no independent verification of the surgeon's claims.
Other sources state that it was green, which is hard for me to believe. How could a plant grow with no light inside a lung? Is this actually possible, or just a news report that has been widely circulated?