Some skinny body types or people who do not overly pronate can handle huge amounts of miles. It also depends on how you approach training. If you start with running too many miles per week or run too fast you will increase your chance of injury tenfold. The better course is to run consistently for around six months at a slow pace and for no more than an hour, and then take your training up a notch.
I used to run 50k races with 10k feet of climbing. The worst injury I got was broken ribs from a fall.