Is this melanoma?

My darling little red-haired girl, Mattie, aged 4, has a black spot on her lower lip that has not been there long. I just compared photos of her taken over the past year and did not see it until now. It looks very scary to me--off to the vet tomorrow.

Has anyone dealt with melanoma on their dog? If so, what is your opinion of this spot?

Here she is last summer with no spot:

And this is what is there now--look just under the two lower center teeth (incisors) and just to the left. The spot is very black just like the photo shows.