Questions about melanoma?

I recently noticed a mole on my fathers shoulder. I asked him how far back he got it, and he said a little over a year ago. I immediately thought of melanoma. I looked up the symptoms online, but I am uncertain. He has a doctor’s visit soon, but I want to know if it might be malignant. It is bigger than 6mm but it is perfectly round. Its just one color, a light brown with some red around the border(not too much).He says it doesn’t bother him, no itching or pain.What do you guys think?