About the size of a quarter open sore on my dog's chest?

[TalisaT]

It's been on his chest on the right side for about 2 weeks now. It started as like a lump then as he itched it's become open and a sore that has scabbed over. It feels thick to the touch and it about a quarter size in diameter. I am taking him to the vet tomorrow but I just wanted to see if I could get any ideas of what it may be first? It feels like it's topical, not too deep but it is kind of a unique sore so I'm quite curious. He doesn't seem to feel sick about it, but you can tell it hurts him a little bit? Any facts is helpful : ) Thank you

[TheMoonSpirit]

It could be a tumor. but like you said, vets the place to go.

x]