According to the Detroit Free Press, Detroit Lions running back Jerome Harrison was scheduled to undergo surgery at noon today for a brain tumor that was discovered by Philadelphia Eagles team physicians. There's no news in regards to if the operation is complete or Harrison's status, but head coach Jim Schwartz did visit Harrison in the hospital, and multiple teammates plan to do so as well.
The report cites Comcast SportsNet Philadelphia, who reported that Harrison had complained to team physician Gary Dorshimer that he was experiencing recurring headaches, and this led to Dorshimer ordering an MRI for Harrison, which reveled the brain tumor. On top of that, multiple players described times when Harrison was experiencing headaches in practice, and made the point that you don't often think about that kind of thing when it comes to football; you think about concussion-related symptoms, a hard hit to the head and things of that nature.
It's a scary situation all around and a testament to the fact that players need to not always think about their future in the league but their future overall, and remember they can experience regular, non-football player injuries as well.