So my dog got a little bump on the inside of her rear right leg two weeks ago that looked kind of like a raised scab. It has doubled in size in the past two weeks and is now red and round with what looks like a little horn or scab in the middle. My first thought was hystiocytoma, but it doesn't really look like photos I've seen of one. I'm going to the vet to have it biopsied next week but any thoughts in the mean time? I'm hoping it is just some random growth and not a mast cell tumor. Has anyone seen a red blister looking bump on their dog with a rough spike of scabby skin in the middle?