What is the likelihood of a removed mildly atypical mole developing into melanoma? 2 years post-op mole removal.

I had a mole removed two years ago & assumed all was fine. My doctor called this week & told me that after reviewing her files, the mole was in fact mildly atypical with a deep margin, and she’s like to schedule an excision to have clear margins. She said it wasn’t cancerous and she was being overly cautious, but my concern is that it was initially removed two years ago- couldn’t something have developed and spread in that amount of time? Starting to panic a bit...