Dad has had a few spots removed over the years, mostly head as he never wore a hat or used sun protection. Now he has a spot on his arm that appeared 2 weeks ago and he noticed it growing fast over the past few days. He is trying to get in touch with his dermatologist. Does melanoma appear fast? Does it grow fast? It is a dime size spot. He was at the dermatologist a few weeks ago and he said they would watch it but not to worry but now it is growing.