It is true, but it hasn't grown, it has just remained green. This has happened before:http://news.nationalgeographic.com/news/2009/04/090415-russia-firman-video-ap.html?source=rss
I call bullshit. How would a tree grow with no sunlight?
http://www.aftonbladet.se/kropphalsa/article4924316.ab
This is from a highly respected swedish newspaper, those here from sweden can confirm the validity of the story. The article also mentions yet another that had a small branch of a tree in the lung.
The first one had got it there when he tried a survival course in which he had to eat from a tree, the other got it there when she was a child (I think).
Both had the branches there for a very long time (several years, or even decades).
Since these are swedish headlines I don't know if they have been reported elsewhere for a english translation. (and why do the spellcheck think english is bogus?)