I have a 13-yr old yellow Lab neutered male with sudden onset of firm circumferential swelling at the base of his tail (about the diameter of an orange) that does not appear to be terribly painful, reddened, or tender. There are no obvious wounds or abrasions, insect bites, or signs of trauma. I have photographs if that would be helpful. Thanks very much for any ideas or suggestions, differential diagnoses, etc.
Symptoms:
Lumps And Swellings
Attached image (click to zoom):
