I have a 12 year old red heeler/pit mix and
She just had a mast cell tumor removed. I'm sorry to hear your pup has the same. I agree it needs a biopsy to confirm it is cancer and hers was. They grade them from 1-3. 1 being non cancerous, 2 in the middle, and 3 full cancer that has spread. Mine came back as a high level 2 and the vet said it had metastasized or spread although he said they had clean margins which means they got it all at the source of the tumor however the fact that he said it spread means the lab believed it went to other parts of her body. The lab report estimated a 4 month life expectancy. Just above her armpit by a front leg. It was pretty harrowing once removed since it was in a high motion area and the stitches wouldn't hold. I had to wash it with chlorhexidine and pack it with sugar 3 times a day. It finally healed and it has been 7 months and she is doing great. I give her one Benadryl and one tagamet twice a day. I don't know if this helps but there is some solid info on the internet that in studies it shows promise. Vets will likely discount this info as B's but it doesn't hurt to try. Mast cell tumors cause the body to create histamine at levels about 50 times normal. This causes the body to get all out of whack and for the stomach to create excessive acid causing ulsers and such. The Benadryl and tagamet combo helps reduce the effects which makes sense. I don't ever post but just going through this I wanted to share this and hope your pup comes out of this ok. It's rough when your animals go through something like this. They mean so much to us. Good luck to you.