I don't think you can actually retrieve the end, I think you have to replace the key cylinder. Cause I used to have an old VW Golf that had a broken piece of key in the ignition, driver's door, and hatch. The only crappy thing was about 3/4 of the key was in the ignition, so your keys would fall out all the time, and you had to use a different fraction for each other lock. So besides the long story, AFAIK, you actually have to replace the cylinder and you cannot take the key out.
