Is it possible to have unharmful skin cancer?

[Cut.to.the.Heart C]

I think my brother has skin cancer of some sort.
He's had this mark ever since he was a little kid on his right upper arm.
It hurts when people touch it and it looks like I guess a blue mole.
It's grown a little with time but nothing has come of it.
He's 18 years old now and it first showed up when he was maybe 5 years old.
I don't have a picture of it but it looks kind of like the third mole in the normal mole section except it's flatter and it isn't round and it kind of gets lighter around the edges to where it kind of disappears into the skin or something.

http://www.chw.org/display/displayFile.asp?filename=/Groups/PediatricHealthInformation/Dermatology/ep_0137.jpg

Also, my mom isn't big on going to the doctor's office I've been once in my life and I'm 16 years old.
She doesn't like to do anything until it's pretty much life threatening.
She thinks it's just a mole or birth mark.

[mevsmaradonavselvis]

Sadly there is no such thing as an unharmful cancer