I agree with this statement, and I would add that perhaps even a major life stress could cause spread. I went years before I experienced spread. I even had surgery on the original limb (knee) without spread, and then years later slowly the progression started.

With others spread is more rapid, or on the other hand, nonexistent. It's crazy. It is my understanding that the incidence of spread is rather low. So perhaps there is some sort of good news.

Try not to marinate on the idea of spread. Perhaps it will never happen.