The vet told us that the lump on Jackson's tail was just a fluid-filled cyst, and not to worry about it unless it grew or became too heavy for him to hold his tail up. Jackson had a fairly long tail and the lump was about in the middle.
So we ignored it for a while, checking it every once in a while to make sure it wasn't getting bigger. He flicked his tail back and forth as if the lump weren't there, as normal, so we didn't worry. You can sort of see the lump in this photo:
Then one night a few weeks ago, he walked into the living room with his tail up at the base but bent in the middle, like a paper clip. We made an appointment for him at the vet. It wasn't good news: the lump was probably cancerous. However, they said tumors in the tail are usually a fairly benign and static type, so, again, we didn't have much to worry about. They'd have to remove the tumor, which could mean they'd have to amputate his tail.
This made us a little sad. Jackson has always had a very long tail in proportion to his body:
...even when he was a kitten:
We were sad because, while we wanted him to be healthy, you never know what value cats place on their tails. They seem like very vain animals (as much as they can be) so I figure it would be like losing your nose or something: you'd survive, but you might not feel like the same person.
His surgery went well, but they did have to amputate his tail, and the vet sent a piece of the tumor to a pathologist to make sure it was the type he expected. We brought him home and he seemed pretty up, despite having a bandage on his tail:
He roamed around the house as normal and didn't seem to bother his bandage much. (The vet told us to watch out for that because cats were notorious for picking at their tails if something was on them.) That lasted a whole day: Thursday night before turning in I went looking for him to make sure he was okay, but before finding him I saw a bandage without a tail sitting in the middle of the kitchen floor.
Jackson was stalking the next room, back and forth, and when his unencumbered tail his something he'd flinch a little bit but keep on going.
I should explain here that the vet used metal sutures to keep his tail closed. He'd used this successfully on many cats before because they tend not to chew on them. (He explained later it would be like you or me gnawing on a clothes hanger. So the end of his half-shaved tail looked like some sort of medieval weapon, with metal spikes sticking out. (No photos, sorry.)
The wound had oozed a little blood but it wasn't actively running. We tried to bandage it back up but he was too ornery, so we took him to a vet that we thought was open 24/7. We got there five minutes before closing (midnight) and, in hindsight, staff clearly wasn't happy about doing this work even though they would've charged an arm and a leg for it.
One of the vets looked at his tail and said the sutures were still in good shape and should be fine until morning when we could take him to our normal vet. To prevent him from chewing he got a stiff plastic collar, and we took him home.
After settling down we closed him in our room and went to bed, only to be awoken a half-hour later by a fierce cry. Barb turned on the lights and he was running around the bed, trailing blood. We'd later find out he ripped out and swallowed one of his sutures (it showed up very clearly on the x-ray). So we found a 24/7 animal hospital and rushed him over there, wrapped in a red towel and crying much of the way.
Ninety minutes later (now about 3:30) he had a new bright green puffy bandage that the vet said should be fine overnight. He was a little suspicious of the metal sutures because he hadn't seen them on a tail before, and warned that the skin at the end of the tail had ruptured and that they'd probably have to take another vertebrae from the end of the tail to close it up properly. He said they'd be able to do the work if our normal vet wasn't, but they'd probably charge twice as much.
So Barb took him the next morning and, despite it not being a surgery day, they called in the vet who typically does surgeries to re-operate. They were able to close the tail up without taking any more off, and used normal sutures instead of the metal ones.
By the time we picked him from his second surgery up the pathologist's report had come back.
More bad news: instead of being the benign tumor they'd expected, it was actually an agressive type of tumor called an osteosarcoma (bone cancer). The vet -- who may have started practicing before I was born -- was very puzzled at this because he'd never seen this type of tumor in a tail: typically it starts in one of the legs which then need to be amputated to stop the growth. It's also apparently more common in dogs than in cats.
So while the pathologist's prognosis came back as "guarded to poor" the vet said he wasn't that pessimistic since they were able to amputate and he didn't see it on the x-ray anywhere else in the body.
In the intervening time he's done pretty well, getting one scheduled bandage change (no photos) and then an unscheduled one because he was picking at the previous bandage. His tail now looks like a Dupont Circle fireplug because of the pink bandage at the end:
And as you can see he's got a collar now, which he absolutely loves. It doesn't entirely prevent him from picking, but it prevents the casual, "Hey what's that?" ones stemming from cats having almost no memory.
So now we wait and see and hope he's okay.