If you do have biopsy or surgery done, be sure to medicate with Benedryl for a full 24 hours prior to and after surgery. When messing with mast cell tumors, they can release histimines that can cause the cancer to spread -- using Benedryl helps minimize the body's reaction to them. Also, if removing more than one, the vet should use a new set of sterile instruments for each removal as the "contaminated" instruments can also spread mast cells.
I sincerely hope it is not a MCT, but in case it is, caught early, removal generally has good results.
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