For six days, I applied a swath of Xxterra Bloodroot paste. The effects of the bloodroot were ... alarming, but it seems to have (mostly) done the job. I captured almost daily photos of Izzy's sheath to show how dramatic the treatment turned out to be. One or two of the photos are quite ugly, so zoom past those if you're squeamish.
If indeed the sarcoid is still there, Dr. Tolley had a few other suggestions for removing it. I'll let you know next fall what we decide to do. For now, it's business as usual.