So it's aggressive, WTF?

What does that mean? I heard it the first go round- it was medium to fast growing, and aggressive. OK, fine but we cut it all out, (we thought) then. So now we discover that something that has been in the surgery site, (appeared right after surgery) and is agressive as well. Now I am scared. What does this mean? Thank God all will be revealed tomorrow. It will be soon enough then. Good night.