I have a mole that changed colors..?

I have had a beauty mark on my arm ever since I was little. I noticed a few weeks ago that it has been changing color..it is a dark brown beauty mark that is spreading out in a lighter brown now.

I am meeting with a general surgeon this week..but I was wondering if it is skin cancer is it automatically melanoma since its 2 different colors?

Im really nervous…if the doctor does a biopsy how long does it take for the results?

Thank you!