Charlie Villanueva, an NBA player, recently played against Kevin Garnett. During the game, Villanueva claims Garnett called him a cancer patient. Garnett, for what it is worth, said he called Villanueva "a cancer", which isn't as far fetched as it sounds. According to urbandictionary, the term cancer "[is] often used as an insult when referring to someone who is a pathelogical [sic] source of trouble and discord within a group."
Now, who knows what happened and what did not, but I can see someone exaggerating because they are annoyed. Either way, the point is he came out and put it out there, and as we know about Twitter, there is no undo button.
If this guy's name sounds familiar, it is because he is the same guy who was benched for tweeting during halftime of a game in 2009. I blogged about that here. I would think the guy would have learned his lesson about Twitter, but nope. If it is getting in the way of your professional life, perhaps it is time to let someone else serve as your filter.