Rex's battle with a poisonous spider bite - June-6-2011

In mid May I discover some faint discolorations on Rex's right thigh. It first looked like dirt which made sense since he falls down quite a bit. I tried to wipe it clean but it did not come off. It was so faint and hardly noticeable that I did not make too much of it, something that turned out to be a huge mistake.

Two weeks later I noticed a tiny hole in the middle of this area and a drop of blood came out. Again I thought he had fallen an punctured a small hole in his skin. I wiped the blood off and nothing else came out. A couple of days later I again saw blood dripping from this tiny hole. I called the vet and she told me to keep an eye on it for any changes.
A couple of days later I saw 3 more holes and small drops of blood. This  was a Saturday afternoon and I called the vet again. She asked me to come in on Monday so she could take a closer look. That Sunday evening it got much worse. While cleaning the area the skin broke between the holes. It was tin as paper. I then realized this is not good something is eating his flesh!
Monday morning we went to the vets office. They stitched up the ripped skin as best they could, took a tissue sample and sent that of to the lab. They suspected an insect bit or cancer.
I was pretty sure it was not cancer since Rex has been on B-17 for many years and I don't know of any dog or human that have gotten cancer while taking B-17. It will be a first.

Here is Rex after his surgery. The wound is stitched up and he's knocked out.