I feel your pain!
I'm very sorry to hear about Mia - I will definitely keep her in my prayers. I just found out this week that the tumor my Rocky had removed was cancer as well. The doctor gave me several options and she was very hopeful. I did a search on google about mast cell tumors and there is tons of info out there. I would suggest finding out the best and worst about it. I know that it's not something that you can ever be ready for - but at least you will have knowledge about it.
As for the co-workers, don't worry about the tears you shed in front of them. Unless your a boxer owner - no one knows the compassion and love that one can have for these dogs. They are the best dogs in the world.
Stay strong and please keep us posted.
Chell - Rocky's mom