I hope this helps
oh mia, I'm so sorry you have to go through this. I totally understand how you feel. Our 11 year old Boxer mix had a mast cell tumor grade 1. They removed 1in radius of skin and muscle. Then they did tons of test, and they removed the lympgh nodes. Thankfully they cought it right before it spread. I tell you at first I was so confused and overwhelhmed. The best thing you can do is find out as much information as you can regarding mast cell tumors. Theres alot of information on the net. This way when the doctor explains you can understand.
One thing though be optomistic, if she has a 1st grade tumor that's the better one to have, it's less agressive. And yes it's going to be rough, because they look so sad and yes they look like patches, but if you keep their spirts up they begin to feel a little better.
Just remember that you are the best parent that she could have had and that you made her time here the best, so be there for here in this confusing time. And it will bring you comfort to know that she has had a great life with you.
Proud parents to Kylie and Chato
(Kylie - girl rev. Brindle, natural ears, docked tail)
(Chato - boy white boxer/mix)