Really bad things don't change that slowly. I have a large mole that I don't like that I always ask whatever doctor I come in contact with (whether mine or my husband's :-) and get the same answer, probably nothing. If they look at it for a bit and then decide it is probably nothing, then it's at least probably nothing serious. I have asked dermatologists about mine and also a surgeon removing "things" from my husband's shoulder, tiny things (mine isn't tiny).

There are all kinds of skin diseases that are just problems with "coloring" or things that require staying out of the sun or using a cream, etc. My girlfriend has one of those.