Squamous cell cancer on sheath

Hey,
Yesterday I had to take my gelding to the vet for her to remove a growth on his sheath. It started several months ago when a vet came to the barn to clean sheaths. She found a sore on my little guy with instructions to keep an eye on it. It never healed so we called the vet again and she gave him antibiotics.
It never healed and in fact, it began to grow.
The vet believes that because his sheath is white that he had developed a squamous cell cancer.
We will know in a week if 1) she got it all and 2) what type of cancer it is.

That's too bad...I sure hope he's ok!
I went out to do my first sheath cleaning yesterday....and was foiled, as he seemed to know I wanted to clean it and didn't drop it for the hour+ we had him tied up! Any tips how to get them to drop?? He has white skin too, so thanks for the heads up to keep a watch on that.

I've been working on that especially now that he's had a growth. What I've been trying to do is "tickle" or rub it down. At first, he was cow kicking but now I've got him to drop about a third of the way down. I'm hoping with enough practice he'll drop it when I touch him.
If anyone else has an idea of how to "teach" him to drop his sheath, I'm all ears. Not something I'm excited to clean but I'm not willing to have a untented cancer grow on him either.

Woo Hoo, I think I figured out how to take care of his sheath without getting cowkicked!!!
He did have a squamous cell cancer and the pathology said the vet got it all. Good news. I've been able to touch but not clean, so I decided today was the day!
I got my SWAT jar, halter him and slowly asked him to drop it. Mind you, I had his tail and kept a snug hold of it and the lead was laying across his back, so if he did go to cowkick and the tail pulling didn't work, I could grab the lead and disengage him away from me.
I found a spot on his buttock that actually relaxes him. He more or less let me SWAT him and he dropped it long enough for me to inspect it carefully.
I've also decided that I need to keep sunscreen around it. So I've bought zinc oxide, (diaper cream) that will help block the sun.