Thanks guys, he's almost fully roaned, but I did get some information from a lady at the barn yesterday and she said most grey horses will get them and it's good to keep checking him. She also has a grey and he has them but they don't bother him, so I'm not too worried yet I'm just being an over protective horse mom 😅 This info helped a lot, thanks again!
Usually melanoma are stimulated by some irritant, like ticks for example. Grey horses tend to be more prone to get melanoma, but not all of them will, especially if irritants are kept in check. Also remember to feed a balanced diet especially minerals. Unfortunately animal feeds are notorious for harbouring chemical residues and some of them are bio-accumulative.
Not all grey horses will get them, mine hasn't and he's 29 :) if you are worried keep checking her over, a horse I worked with had them and we occasionally put some cream on if they started weeping but they weren't operated on