Bay horse with Malignant Melanoma

[Jazzie]

Has anyone had experience with Bay horses with melanoma?

My vet has left it at “keep a eye on lymph nodes” and wait and see. At the time of removal he wasn’t however very positive if the histology came back malignant.

Horse is a just gone 8yr old Irish/Tb cross. Presented with a small lump on the right shoulder, monitored for 2-3months, was constantly weeping, and rubbing on the covers. Had vet out to remove it - it was roughly the size of the end of my thumb.

Histology diagnosis - cutaneous melanoma, that shows local infiltrative/invasive behavior. Due to high pigmentation bleaching was done.
Notes: Neoplastic cells have variably distinct cell borders, nucleus with finely stippled chromatin and variable distinct magenta nucleoli. There is marked anisokaryosis and moderate nuclear pleomorphism.

Now I’m hoping anyone who has experience can chime in a explain the above in a littler more detail for me (my vet wasnt very helpful other than “its a wait and see situation” )

I do know that its a bit more odd for a bay horse to have these.

I was hoping to sell the horse this coming season once he had hit 1* level eventing and/or level 3 dressage. But I’m not sure of two things
a) asking him to compete if he isn’t 100%
b) selling him on if the chance is high that he will end up riddled and the person who buys doesn’t do the right thing soon enough, or doesn’t take the right course of action should more come up. I also would have to disclose this when selling, which will highly likely make it not worth selling him for anything more than a low level plodder.

[Bluey]

We had a feral horse that at 8 had some marble sized bumps show up on his mouth, from the corner and up his face.
The vet cut them out as far as he could tell, until clear borders, sent them to the lab and the report came back similar to yours, adding that they were generally very aggressive and the prognosis poor.

Well, he never had any more show up and lived to 20, when his bad knees, rickets from being a feral horse growing up in the wild in a drought caught up with him.

Maybe your horse also won’t have any more show up?

[JB]

The bigger question is- how clean and wide were the margins of the removal tissue?

[poltroon]

There is that new vaccine for melanoma. I understand it’s expensive but it seems like it might be worth investigating for a horse like this.

[oldernewbie]

[QUOTE=poltroon;8920178]
There is that new vaccine for melanoma. I understand it’s expensive but it seems like it might be worth investigating for a horse like this.[/QUOTE]

I am not a vet, so take this with a grain of salt, but I do not believe the vaccine works for malignant melanomas. The melanomas that occur as part of the graying process are generally benign and the vaccines are targeted to suppress one substance that’s needed for their growth. The disease process for malignant melanomas is different. At least that’s what I get from reading Philip’s 2013 article.

OP, I am sorry this has happened to your horse. Maybe a consult with a university vet would help you understand your options and the horse’s future?

[gnu]

Been there done that, but horse was in his 20’s. Bay gelding. Prognosis was 6 months, but he had a decent 2 years. Below are the comments from the pathologist.

“The mass is a malignant melanoma. Equine cutaneous melanomas can remain static and benign
in behavior for a considerable period of time, often years. Some of them eventually undergo malignant
transformation, become locally aggressive as described in this case, and they can then metastasize via
lymphatics. These tumors are also frequently multiple.”

[Jazzie]

Thanks everyone.

The margins were only noted as “clear and wide”

I noticed today he had some “off” sweat marks - to the top, and to the right of the scar from the removal of the lump. After a trailer ride to a arena today, when he had disembarked he wasn’t sweaty anywhere else (visible) but the two marks on his shoulder near the sight. And I believe (with trying to tell myself I may be looking for something that isn’t there) somewhat enlarged glands etc in the throat latch. I took some photos to compare with historic photo’s and once I’ve done that tomorrow and it is conclusive, I may call the vet back for a review/palpation and referral to the university.

[AKB]

I think you need to go to a university/vet school clinic and see whichever vet knows most about melanomas. If you are within a 100 miles of a couple of vet schools, look at the names of the vet school faculty and see who has some publications on melanoma. I have always heard that melanomas are more aggressive in horses who are not grey. I don’t know if it is true. Where are you located? Perhaps some people here could say where they have gone for melanoma vaccine and trials of new meds? This sounds like a young, nice, horse who should get an evaluation from a top melanoma vet.

[Jazzie]

I’m in New Zealand, with only the one university. So I am a little limited.

[Foxtrot_s]

Very sorry to hear this. Have had the problem in grays which is common.
No, he will not be a sales prospect. I’d maybe lease him out if he is suitable, but I’d need to keep tabs on him for future problems and be able to make the hard decision if the time came.

[Gfury]

I realize this post is old, but I just joined and wanted to address my horse’s melanoma. He is a dark bay 17h and I notice a tiny lump in his ear. The vet said to watch it. Within a year, it grew quite large. The vet then decided to remove it. At first she did not know what it was until they sent it out for biop. The report came back melanoma but did not get all and it will come back. Sure enough, it came back. The vet also said at this point don’t start cutting at his ear or eventually he will have no ear. So, now he has the lump at the base of his of his ear. The vet will be coming out and will check that one as well. If there is a vaccine that will remedy this, can someone let me know. I keep reading and reading to get more information.

[Hej]

Those of you with bay horses who have melanomas might want to look at the U of Florida Vet school website. They have a vaccine trial for greys with melanoma.

One of my boarders is a bay w/malignant melanoma, I believe this was one resource his owner used to get him into a vaccine trial. I’m not sure whether it’s the UF trial - she did an enormous amount of research looking for help.

The vaccine is produced from the cells of the individual horse’s tumor. I’m sorry, I can’t recall the name of the company that does the preparation. At this point it would only be available through a trial program, but my boarder’s vet is administering the vaccine protocol under the direction & guidelines of the trial program. So far the horse is looking like he’s having a good response.

There’s a small but very interested group of veterinary oncologists spread around the world who are looking at m/m in bay horses, as it is relatively rare but so aggressive when it occurs.

[zoehesed]

I have a large aged (early20’s) chestnut pony mare that I recently noticed a lump neap the base of her tail (on the tail) that is about the size of a large grape. It looks like a malanoma to me based on what I’ve seen on gray horses but she’s a chestnut…?

Is melanoma aggressive on chestnuts like in bays (as people are saying on this thread)? I will be having the vet out soon to investigate things more but would love to hear anyone’s opinions on this might be?

[csaper58]

@Jazzie

I’m in New Zealand, with only the one university. So I am a little limited.

Will vet school Skype an out of town consult? Is there a vet oncologist you can do a phone consult with?