I just wanted to add my experience. I had a flat, relatively symmetrical but large (bigger than a pencil eraser) mole spring up on my back about three years ago (age 21-22...can't remember exactly). I expressed to my derm that it worried me because of the size and that fact that I couldn't see it well--I had to use two mirrors and kind of twist to see it--but the derm wasn't concerned and wouldn't remove it.
Of course right after the initial examination of it, the mole began to itch on and off (especially in cold winter months). Eventually it got itchier to the point that I was driving my mom and others crazy asking her to scratch it all the time. My mom convinced me that I was just being a hypochondriac any time I expressed concern about it to her, though--"[the derm] already looked at it", "I have lots of those and they're nothing" etc. etc., so that I didn't ask the derm to look at it again even though it had been itchy and annoying for like 2 years! I also thought it had gotten slightly bigger and more raised. I had not noticed color changes, though, or bleeding.
Finally last week I had an annual appointment for other reasons and told the derm I couldn't take the itching anymore. She said the mole didn't look bad but removed it due to the itching. It turned out to be a benign mole with mildly dysplastic features (so, beginning to have some iffy changes).
I just wanted to give my story so that others know that itching does not always equal melanoma (which is pretty much all I found online--Itching=BAD!! CANCER!!). However, I also know that waiting for two years with the itching wasn't really a good idea...so, especially if your mole has become asymmetrical or started bleeding, don't follow my example and just get it checked out

. That way you won't have to worry; and even moles with "warning signs" aren't always the "worst case scenario."