Yes, I think it is necessary as it may very well be cancerous. Has he been neutered? If not, then now would be a good time to do this while he is already under anesthesia. This may also help prevent any more of these "tumors" as they tend to be hormonally related. Both of these are routine surgeries and he should do just fine. Give him something to keep his stool soft for a week or so after the rectal polyp is removed so he does not strain to go. Has this vet been your vet for awhile? Has he been in business for awhile? If so, it should be fine. Word of mouth travels fast when clients are unhappy.
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