Hi Vivian:
From what I'm understanding, the 2mm growth may not have occurred at all.
I'm thinking you do have 2 options and you have to feel comfy with what one you take.
Now I assume you are asking for opinions so here is mine
Since it may not even have grown at all.. or may not grow for another couple of years, I would hold off. However, are your symptoms bad enough that you want to end any further discomfort?
If you are non symptomatic and there is really no growth, I would consider leaving it. BUT, since it is 20 mm already and there could be an irratic growth spurt at some point, then the smaller the easier to remove. Also, the earlier you treat, they younger you are, the easier/faster to heal (that is what I have been told over and over by the docs lately anyway).
My answers are all over the board once I re-read what I typed up there. lol But they all make sense from one side of the fence or the other.
So of course you still have 2 choices and it ultimately falls into your hands and you future.
Read lots on here and find out what others have done and their final results, their ages, the sizes, ect... this will help you in your decision.
Thinking of you!
Rhonda