No Lumpy Bump!

I'm Miriam and this is my service dog Cora. We just had our vet check a mysterious lump and he's very concerned. The vet thinks it's be a Mast cell tumor, which can be malignant or benign. In less than a week the lump has gone from the size of a pea to the size of a Lima bean. This growth speed is a very bad sign. 
It will cost just over $350 to have the lumpectomy. I'm disabled and haven't been able to work in over a year.  I'm desperate for my dog to be well as she is what let's me function at all. Her wellbeing and service are life changing for me. I'm dedicated to her continued good health. Any help however small would be deeply appreciated.