tail tumor

Tail Update: What the Vet Said

So, when I posted that Tristan’s tail lump had mysteriously vanished, I said I would email the vet and check in.

Here’s the email exchange.

Hi Vet,

I went out to the barn on Monday, and Tristan’s wrap had come off when he came in from the field, finally. (It was on for 5 weeks!)

There is…nothing at all on his tail. No stitches, no lump, only a vague maybe-sorta outline where the lump was.

So, I guess it’s all over with? I’m puzzled but glad, I guess. Weirdo horse.

Her reply. The bolding is mine.

It’s our beads! Non-cancerous tumor or not, they shrunk the growing tissue. As an aside, I’m thinking of doing a research project on this. It is very interesting. Glad they are gone and he is well!!

My horse: subject of a research paper, coming soon. If she actually does write it I will absolutely share it.

(For those wondering what happened to the radioactive beads: I, too, am wondering. My best guess is that since they were “bioabsorbable” they did indeed absorb fully and are gone, and that the half-life of the radioactivity was such that there is no concern. I have emailed the vet back to make 100% sure, though. She is SUPER on top of things, so if there were any danger I’m quite confident that she would have followed up.)

At least he is cute.

adventures with the vet · tail tumor

Weirdo horse gets somehow even more weird: tail update

You guys, I do not even anymore.

Monday afternoon, I went out to ride. Yay.

Tristan’s tail wrap was missing. Lo, the miracle of the Elastikon had at last come to an end; it continued almost two more weeks after I first reported it. Goddamn, you guys, seriously.

Anyway: it was gone now.

So, I lifted up his tail, curious as to what it would look like. It had been nearly two months since we put in the cisplastin beads, and one month since I last looked at it, when it looked like a healing scab.

There was nothing there.


You can sorta-kinda see a vague outline of a maybe-lump in the second picture. That’s where it was.
No stitches.
No lump.
Like nothing ever happened.
Certainly not a $750 ordeal with multiple vet checks and a biopsy and a second lab test on the biopsy and goddamn chemotherapy.
I mean, I am not complaining. Really, I’m not. I have an email in the vet basically consisting of ?!?!?! and I am a smidge worried that maybe the beads were supposed to come out? Also, the stitches? But other than that, problem seems to be solved without another vet visit.

So, thus ends the saga of the tail tumor, which was weird from point A to point B.

adventures with the vet · first aid · tail tumor

The Miracle of the Elastikon

My love for Elastikon is well-documented. I firmly believe that at least one roll of this miracle substance should be in every equestrian first aid kit. I could not begin to estimate how many rolls I have gone through in the last few years.

On Sunday, I returned to see Tristan for the first time in nearly two weeks after the wedding + mini-honeymoon. Before I left, I did my due diligence and had conversations with the vet and the barn manager about our tail protocol.

The plan was that his tail would stay wrapped as long as the wrap held. He could then keep it unwrapped as long as he was not rubbing it. If he was rubbing it, the wrap would need to go back on. Since the first wrap lasted about two weeks, I expected that the wrap would come off while I was gone and we would see whether or not he rubbed his tail. I didn’t hear anything while I was away – the barn manager was very firm that she would only call or text me in case of actual emergency, since she wanted me to be stress free.

I arrived Sunday…

Let me contextualize this for you.
Tails are notoriously difficult to wrap, right? We’ve all been there. They are slippery and if you do them too tight it’s super dangerous. So you have to strike an impossible balance on being snug but not tight, sticky but not anything that will actually damage the tail irreparably.
This wrap has lasted almost four weeks. I thought two weeks was an extraordinary gift. Four weeks!!!
Lest you think that the tail is damaged underneath, I checked carefully for chafing and rubbing, and found none. I’m not saying it will slide right off with zero problems, but I don’t anticipate a complete mess when it’s time.
Here’s what it looked like after I took the old wrap off. Not too bad, huh?

In conclusion:


tail tumor

Tail Lump: Final Diagnosis

My horse, the medical marvel. Here’s what the final pathology report says:

The following histochemical stains were performed on haired skin, ventral tail nodule (slide 1; 4 sections): 

Toluidine blue (mast cells): In 2 sections, there are small aggregates of mast cells containing metachromatic granules. 

Throughout all sections admixed with the eosinophils there are moderate numbers of individual mast cells. 


Histochemical staining with toluidine blue reveals the presence of clustered mast cells, consistent with a diagnosis of cutaneous mast cell tumor. Serial deeper sections did not show evidence of Habronema parasites or any other additional findings. Equine cutaneous mast cell tumors are usually benign and often, as in this case, very eosinophil rich. Complete surgical excision is curative. Anecdotally, in some cases even partial excision has resulted in spontaneous regression of the mast cell tumor. 

Amended morphologic diagnosis:
Haired skin, ventral tail nodule: Cutaneous mast cell tumor


If you remember, this was the least likely of the three original possible diagnoses.

What a special snowflake.

Waiting on the vet’s word, about whether excision is the next step and if so, how soon. Given that it is definitely receding thanks to the bioabsorbable cisplastin beads we sutured in this may not be an immediate step.

Either way, seriously? I have been exposed to my fair share of medical weirdness in person, and I am an avid reader of the COTH forums for weird medical stuff, and I have never even heard of this. I even did a search for “mast cell” on COTH and it came up with cancer stories in people and dogs. No horses.


adventures with the vet · tail tumor

Pathology Report

I have to admit, this reads to me like the science-y version of a very elaborate and confused shoulder shrug, but there you have it. It does say that we are still waiting on further testing to hopefully prove or disprove at least one of these possibilities.

I share it here in the dual interests of education and curiosity. If you can interpret any piece of it in a way that sheds light, let me know! If you are just deeply curious about what a highly technical pathology report looks like, wonder no more.

If you just want to read my vet’s layman’s explanation for this, it’s what I wrote up on Friday.

The histologic findings show a severe eosinophilic dermatitis. The top differentials for this lesion are habronemiosis, eosinophilic granuloma, or cutaneous mast cell tumor. Some horses have an atypical eosinophilic response to bacterial infection and some fungal infections such as, oomycetes. No bacteria or fungi are noted. No habronema parasites are seen in the examined sections but additional deeper sections to further examine for residual parasites are pending and additional results will follow in an addendum. Cutaneous mast cell tumor in the horse can be a highly eosinophilic condition with very few mast cells present. The clusters of mast cells required for the diagnosis of cutaneous mast cell tumor are not appreciated in these biopsy sections but histochemical staining to better highlight mast cells are also pending and results will follow in an addendum. Excluding these differentials, the remaining differential is equine eosinophilic granuloma, which is a common skin lesion of uncertain etiology. A hypersensitivity response to insect bites is one speculated cause. Lesions of equine eosinophilic granuloma occur most commonly on the neck, withers, back, and girth region and are often alopecic without ulceration. Early eosinophilic granulomas generally respond to treatment with corticosteroids while chronic lesions may require surgical excision. Strict insect control may diminish recurrences in cases due to insect bites.

I googled “habronemiosis” because what the heck, did a lot of digging, and came up with this slightly more readable explanation:

So…we wait. Some more.

adventures with the vet · tail tumor

Lab Results

Previously on why Tristan is a special snowflake who loves to confound his vet.

Last night at 9:30 pm – bless her – my vet called with the lab results.

Being a vet, she led with “It’s not too bad!”


What follows will be a somewhat cursory summary; the connection wasn’t terrific, and I have not the slightest idea how to spell the actual names of things she was telling me. She will be sending me the full lab report from the pathologist ASAP. (She probably, I don’t know, had to go feed her baby or something last night after getting off the phone with me, jeez.) She also has to talk to the pathologist personally, as all she has right now is the report that arrived by email.

Here, have last night’s sunset to break up text.

Important takeaways:

– the biopsy samples looked weird because they are weird; still no clear diagnosis
– no cancerous cells seen in the samples, and they were both good, clear samples

There are three possibilities for the lump.

The first is essentially a parasite reaction. Apparently there are flies that burrow under skin and cause lumps. There were no larvae seen on the sample, but the rest of the pathology fits this possibility. She had a specific one she thought was the culprit but I did not catch the name, and could not find it even after an hour of Googling. Way to be obscure, Tris. Solution: intensive worming regimen with moxidectin.

The second is just super-weird granulation tissue (kind of like the world’s weirdest proud flesh). I didn’t catch a solution to this. I’m not sure there is one other than wait and watch and make sure it doesn’t take off. At least it’s in an easy place.

The third is a mast cell tumor. These are apparently very rare in horses, and vet thinks this is the least likely possibility for a lot of reasons, chief among them that there were no cancer cells seen on the samples. If it is mast cell, they do not tend to metastasize, so that’s good news. Solution: probably just what we did, inserting the beads of cisplastin into the tumor.

At some point today, vet and I will connect so that she can get me 2-3 vials of epinephrine. Apparently as mast cell tumors break down, they can release large amounts of histamine, which will basically mimic anaphylactic shock. So Tris will get an equine epi-pen just in case, and as the vet said, these are just good things to have around a barn. Vet was antsy enough about this possibility to say to me if I traveled with him I should bring a cooler and these vials. Eep. I reassured her we were going nowhere and he would be watched constantly, and then I seriously considered the possibility of sleeping in the barn for the next few weeks. Except, drat, stupid wedding. Hm.

So, keep on keeping on, I guess? Now that our drama seems to be receding (KNOCK ALL THE WOOD), my focus is back on fitness and setting us up for the winter. If we don’t have a good base and a good schedule heading into winter, we’ll be lost again.

adventures with the vet · tail tumor

The Waiting Game

First, the tl;dr: no news is no news. No clear answers yet.

Yesterday, I said that I had found a lump on Tristan’s tail and the vet wanted to see it ASAP.

First, my apologies if this is a little bit…scattered? I’m going to try to write it out in a straightforward way but my brain as of late has been slipping gears and/or foggy.

I left work a little late, and then was delayed picking up my car from the mechanic, so pulled into the barn right as the vet did. I’d been hoping for an hour or two of decompression and maybe a ride around the field.

sunlight in the valley to break up text

I changed, and brought Tris to the front of the barn for the vet to examine. I adore my vet; she is smart, fierce, kind, and always has an aura of competence and calm, though she’s only a few years older than I am.

First examination: lots of frowning face from the vet. Definitely an abnormal lump: hard, rather large, and not sensitive, as I had already observed. I admitted, deeply ashamed, that I didn’t know how long it had been there. We pieced together between us that it had to have formed and grown this summer, since she took his temperature in late spring for the abscess, and I remembered treating his tail for a rub around that time as well.

We talked a lot, and tried to navigate our way through a couple of best options.

No matter what, we had to biopsy. That led to the first decision. A biopsy in this case meant a 2mm punch of skin from the tumor itself, which was likely to be quite painful.

two nights ago

The vet felt that just the initial visual examination of tissue from the lump would tell us a lot. If it was a melanoma, game over. Gray horses can grow melanomas with no ill effects, but bay horses should not. If it was a melanoma, it was aggressive and nasty and would have to be removed with clear margins for Tris to have a chance.

There was a chance it could also be a very oddly-presenting abscess or another kind of tumor entirely. We talked through the different treatment possibilities for all of the options, and eventually arrived at a plan of treatment. The vet would do two biopsy punches, and after each one she would insert a bead of bioabsobable Cisplastin, two for the size of the lump. If it turned out to be some kind of cancerous tumor, Cisplastin would have been our first treatment anyway. If it turned out to be something else entirely, the dosage was small enough and the location precise enough that it would not necessarily cause problems. She also felt quite strongly that it was a cancerous lump of some kind and that this would both save additional visits and be the swiftest and most effective treatment.

sorry, very blurry picture, but the beads are about the size of Nerds

Vet explained that she often does an epidural to treat tails. Pros: the tail would be completely numb and relaxed and we could work without any worry. Cons: many horses did not tolerate the epidural shot well at all, and there was a good chance that he would become temporarily ataxic in his back legs as well, so we would have to keep a very close eye on him for a few hours.

Here was my first fear-based retreat of the day. I heard “ataxic” and started shaking my head. I pressed and pressed and asked about other options, and we talked through them, and eventually we arrived at a plan. I wasn’t communicating terrifically well but I think she saw how afraid I was and worked with me.

The new plan: a general sedative followed by a local lidocaine shot. Vet had not suggested it as the first option because apparently tails do not necessarily numb easily or well. We would be doing a painful procedure directly behind him, which anyone in horses knows is not an optimal situation for less than perfect numbing.


But I couldn’t say yes to the epidural. I knew that Tristan was generally among the top 1% of best-behaved horses in the universe for medical procedures, and I wanted to give him the chance to keep that designation. So we shot him up with a sedative, and then the vet did a sub-cutaneous injection of lidocaine in a half-circle above the lump.

My second fear-based retreat: I couldn’t watch. I held his tail up and to the side. I kept a hand on his flank to comfort him, and talked to him, but I could not bring myself to watch after the first lidocaine injection. I got ill, dizzy and woozy and had tears prick in my eyes.

I am emphatically not a person who freaks out at blood. I’ve seen some pretty nasty injuries, in person and in photos. This was just a tiny needle. But I couldn’t do it.

So I held his tail. I looked at the ground, or at his head. I listened to the vet talking to her assistant and the lesson in the ring, on canter half-steps. Tristan behaved perfectly. He splayed his feet, sleepy and drugged, and did not so much as try to twitch his tail.

The vet took two punches of skin, and we had our first answer: they were not black, and so unless it was a very odd presentation, it was not a melanoma. So that was a piece of good news. It probably, however, was not an abscess either, as it did not drain. Answers at this point started to get pushed out further, depending on the results of the biopsy.

About halfway through, I started feeling a bit better, and watched the vet put the two tiny beads in and pull the sutures together. Two holes, two beads, two tiny sutures with two stitches each. There was not a lot of blood.

finally took a picture. this is the only one of the actual procedure.
The insertion process was painstakingly careful and slow, and then it seemed to go quickly after that. The vet padded the sutures with thick gauze and then wrapped the tail very gently and carefully with Elastikon. The tail is a tough place to keep clean, and she didn’t want the sutures tickling him and causing him to rub. If the sutures came out and the Cisplastin beads fell out we’d be in a lot of trouble – not just because he wouldn’t be getting treatment, but also because they were, after all, radioactive.

I led him back to his stall, and he slowly woke up over the course of the afternoon, seemingly no worse for the wear.
I had planned on a couple of different things to maybe do that afternoon: give him a bath, take a ride around the field, soak his feet. All of those were now precluded by either his drugged nature or his healing tail. So I brushed him, and I hugged him, and I cried over him. I picked out his feet carefully and packed them with Magic Cushion so I could feel like I was doing something.

Aftercare is simple: keep his tail wrapped. He’ll get antibiotics for 5 days, and we’ll keep an eye on him. Nothing more complicated or involved than that.
And so we wait. Approximately 10 days for lab results from the biopsied lump, and then we adjust plans based on that.
I am…sadness isn’t a good word for it. Numb. Tired. Automated. I sat with him for a long time, and then I went home. I turned down the very generous offer from the barn manager to take one of the ponies out for a trail ride because I didn’t want to ride a horse. I wanted to ride my horse. When I got home I laid down on the couch with a book and a glass of water and fell sound asleep for two hours. I’ve been sort of listlessly wandering since: getting things done mechanically, efficiently, and wishing I were at the barn instead, but not with that burning joy you feel when you can’t wait to ride on a beautiful day. Just because I feel cut loose and Tris has always been my anchor.