I hate to be the bearer of bad news, but it's probably cancer. You need to take them down to your local oncologist and if they catch it quickly, it might save your boot. They might have to cut it out and put in a denim patch, or maybe suede, but your boots are on the slide to the end. Be careful when wearing them, always wear socks, because you really don't want to catch cancer.
3/9/12 at 8:23am