You can cancel the transaction and get a refund on the fees.
I have a suit and the inside of the pants are soiled with urine. I don't think cleaning will get the stains out (I tried very briefly). The reason I purchased the suit is because the jacket could be worn as a blazer, and it's also a 100% cashmere Bijan suit. I could sell the blazer alone and be done with it, or I could include the pants and obviously note that they are stained and include photos. I believe, psychologically speaking, even a buyer who intends to throw the pants away will want to pay less for the jacket than they would have if it were sold as a blazer with no pants. The jacket is now "lesser than" because it's part of a suit that someone pissed in. IMO, I'm going to make more money by selling it as a blazer with no pants.
On the other hand, Spoo just sold a Zegna Couture suit with soiled pants for like $375, but it was a pinstripe suit, which changes the game. He basically had to sell it with the pants.
What would you do?
I would see if the dry cleaner could get it out. I've sent 3-4 pair with good result.