Grey Connemaras and melanomas have been linked for years.
Most experienced owners have heard of the small dark lumps that can appear under the tail of an older grey. What is much less widely known is that we now understand far more about why some grey horses seem much more prone to them than others.
That is where things get particularly interesting for Connemara owners and breeders.
Some Connemaras grey very quickly. They may be dark as foals, dappled within a few years and almost white while still relatively young.
Others hang onto their darker coat for much longer and may still be heavily dappled well into later life.
Those differences are not just cosmetic. Recent research has identified different forms of the grey gene, and they are linked to different rates of greying and different levels of melanoma risk.
Read more about the grey gene in Connemara ponies
Why are melanomas so common in grey Connemaras?
A grey Connemara is born with another colour underneath the grey.
It may start life bay, black, chestnut or another colour, then gradually develop more and more white hairs as it gets older.
That greying process is linked to changes involving the STX17 region of the genome. The same genetic mechanism that causes progressive greying is also associated with a much greater tendency to develop melanocytic tumours.
These tumours become increasingly common with age.
Current evidence suggests that more than 70% of grey horses over 15 develop melanomas, although figures vary between studies and populations.
That sounds frightening, but it needs context.
Many grey horses develop one or more small melanomas that grow very slowly and cause little trouble for years.
Others develop tumours that enlarge, form clusters, ulcerate, interfere with normal function or spread elsewhere in the body.
So neither extreme is particularly helpful.
It is not true that every melanoma in a grey pony is harmless.
But finding a small melanoma does not automatically mean the pony is seriously ill either.
What does a melanoma look like on a grey Connemara?
The typical melanoma is a firm, dark lump in or just beneath the skin.
They are commonly found under the tail, around the anus, around the vulva or sheath, around the lips and head, and around the throatlatch.
Some remain as individual small lumps. Others gradually increase in number or grow together into larger masses.
Not every lump on a grey Connemara is a melanoma, though.
If you find something new, particularly if it is growing or changing, it is worth having your vet look at it rather than assuming.
Can melanomas occur inside the body?
Yes.
Melanomas are often noticed first on the skin, but melanocytic tumours can also occur deeper in the body or spread internally.
That can be much more serious because there may be little to see from the outside.
Published cases have documented melanoma involving internal structures including lymph nodes, the chest and other tissues.
This is one of the reasons it is better not to dismiss every melanoma as “just one of those grey horse things”.
Are melanomas in grey horses cancer?
This is where the terminology gets messy.
A melanoma is a tumour made up of melanocytes, the cells involved in pigment.
In grey horses, many of these tumours behave slowly for a long time. Some remain small and relatively inactive.
Others become more invasive or spread.
Veterinary literature therefore distinguishes between different types and patterns of melanocytic tumours rather than treating every lump as identical.
For an owner, the practical point is simpler:
Some melanomas cause very little trouble, while others become significant disease.
You cannot tell which way every small lump will behave simply by looking at it once.
The surprising part: not all grey Connemaras have the same grey genetics
This is probably the most interesting development in recent years.
Scientists have identified two important grey variants known as G2 and G3.
G2 is associated with slower greying.
G3 is associated with faster greying.
The difference appears to matter for more than coat colour.
Horses carrying G3 have a higher incidence of melanoma, while G2 is associated with a much lower incidence.
And importantly for this article, the G2 variant has been identified in Connemara ponies.
Does a Connemara that goes white quickly have a higher melanoma risk?
On average, yes.
The faster-greying G3 variant is associated with a higher incidence of melanoma.
The slower-greying G2 variant is associated with a lower incidence.
That does not mean you can look at a young Connemara and know exactly what will happen to it later.
A pony that greys quickly is not guaranteed to develop troublesome melanomas.
A slow-greying pony is not guaranteed never to develop them.
But the speed of greying is no longer just an interesting colour difference. We now know it can reflect underlying genetics that are linked to melanoma risk.
What exactly are G2 and G3?
Both are forms of the genetic change that causes a horse to grey.
G2 involves a duplication of a section associated with STX17.
G3 involves a triplication.
In practical terms, G2 is associated with slower greying and lower melanoma incidence, while G3 is associated with faster greying and higher melanoma incidence.
A horse only needs one grey allele to turn grey.
That means you can see combinations such as N/G2, N/G3, G2/G3 or G3/G3.
The genetics are more complicated than the old idea of simply “grey” or “not grey”.
Can you test a Connemara for G2 and G3?
Yes.
A grey copy-number DNA test can now identify many of these genotypes.
That could be useful for breeders who want to know whether a pony carries the slower-greying G2 variant or the faster-greying G3 variant.
There is one limitation worth knowing.
Some results with four detected copies cannot currently be distinguished as either N/G3 or G2/G2, so they may be reported as unresolved.
And this is not a test that can tell you, “This pony will develop melanomas.”
It is a genetic test that can tell you which grey variants are present and therefore whether the pony belongs to a higher- or lower-risk group.
That is useful information, but it is not a prediction of an individual pony’s future.
Does the colour underneath the grey matter too?
Possibly.
A grey pony does not lose its original colour genetics just because its coat turns grey.
A pony that was genetically black before greying is still genetically black underneath.
The agouti gene appears to matter here too.
Research has found that grey horses with an a/a agouti genotype have a higher melanoma risk than some other grey horses.
That does not mean every black-based grey is destined to develop melanoma.
It simply suggests that melanoma risk is influenced by more than one part of the colour-genetics picture.
If A/A, A/a and a/a mean nothing to you, our separate guide to the agouti gene in Connemara ponies explains them in plain English.
Are melanomas caused by sunlight?
The typical melanomas seen in grey horses are not thought to develop for the same reason that many human melanomas do.
Their strong association with the grey genotype points to a genetic mechanism involving pigment cells rather than simply UV exposure.
So keeping a grey Connemara out of the sun is not considered a way of preventing the melanomas associated with greying.
Sun protection can still matter for other reasons, particularly on areas of unpigmented skin, but that is a separate issue.
When should you get a lump checked?
You do not need to inspect your grey pony every morning expecting to find something sinister, but it is worth knowing what is already there.
If you find a new lump, especially on an older grey, keep an eye on it.
A veterinary check is particularly sensible if the lump gets noticeably bigger, changes shape, starts bleeding or ulcerating, appears to be causing discomfort, or is in a position where further growth could interfere with normal function.
A simple dated photograph can also be surprisingly useful. It is much easier to judge whether something has changed when you have an earlier picture to compare it with.
Should a small melanoma be removed?
Sometimes. Sometimes not.
There is no rule saying that every melanoma should be removed as soon as it appears.
Equally, the old approach of leaving every melanoma alone until it becomes a problem is not always ideal.
Small, clearly defined melanomas in accessible areas can sometimes be successfully removed.
Once tumours become large, numerous or intertwined with surrounding tissue, treatment can become much more difficult.
So finding a small lump is a good reason to have a conversation with your vet, even if the eventual decision is simply to monitor it.
How are melanomas treated in horses?
Treatment depends on where the tumours are, how many there are, how quickly they are growing and whether they appear to have spread.
Surgery is one option for suitable individual tumours.
Other approaches include local chemotherapy, including cisplatin-based treatment, and electrochemotherapy.
Laser surgery, cryosurgery and other treatments are also used in some cases.
There is no single treatment that suits every horse or every melanoma.
What about cimetidine?
Cimetidine is one of those treatments that has been talked about around yards for years.
Early reports suggested that it might reduce tumour size in some horses.
Later studies and clinical experience have been much less convincing, and the evidence has been inconsistent.
So it should not be treated as a proven cure for equine melanoma.
Can non-grey Connemaras develop melanomas?
Yes.
Grey horses are much more strongly predisposed, but melanocytic tumours can also occur in horses of other colours.
So being bay, black, chestnut, buckskin or another colour does not make every suspicious pigmented lump irrelevant.
What does the new grey research mean for Connemara breeders?
This is where things become genuinely interesting.
Grey is deeply established in the Connemara breed.
Until recently, a breeder thinking about colour might simply have considered whether a mating could produce grey.
Now there is another question:
Which grey?
The discovery of G2 and G3 means there are grey Connemaras that may carry quite different genetic risks while still ultimately becoming grey.
Because G2 has been found in the Connemara breed and is associated with slower greying and lower melanoma incidence, breeders now have the possibility of taking that information into account when planning matings.
That does not mean colour genetics should suddenly become the main reason for choosing a stallion or mare.
Type, temperament, soundness, performance, pedigree and genetic diversity still matter far more than coat colour.
But if two otherwise suitable breeding animals carry different grey variants, that information may now be worth knowing.
A few years ago, breeders simply did not have it.
The useful takeaway for grey Connemara owners
Owning a grey Connemara does not mean spending its life waiting for melanoma.
It does mean being aware that the risk rises with age.
Know the common places melanomas appear.
Notice new lumps.
Keep an eye on anything already there.
And if something changes, get it checked.
For breeders, the newer G2/G3 research adds another layer.
We have known for generations that some Connemaras grey much faster than others.
Now we are beginning to understand that how a pony greys may matter as much as the fact that it greys at all.
Frequently Asked Questions About Melanomas in Grey Connemara Ponies
Do all grey Connemaras develop melanomas?
No. The risk is high in older grey horses, but not every grey Connemara will develop melanomas, and not every melanoma becomes a serious problem.
How common are melanomas in older grey horses?
More than 70% of grey horses over 15 are reported to develop melanomas.
Where do melanomas usually appear on grey horses?
Common sites include beneath the tail, around the anus and genital areas, around the head and lips, and at the throatlatch.
Does a Connemara that greys quickly have a higher melanoma risk?
Fast greying is associated with the G3 grey variant, which is also associated with a higher incidence of melanoma. The slower-greying G2 variant carries a lower incidence.
What are G2 and G3 in grey Connemaras?
They are different forms of the genetic change that causes greying. G2 is associated with slower greying and lower melanoma incidence. G3 is associated with faster greying and higher melanoma incidence.
Can you DNA test for G2 and G3?
Yes. Grey copy-number testing can identify many G2 and G3 genotypes, although some results cannot currently be completely resolved.
Can a DNA test tell whether my Connemara will develop melanomas?
No. It can identify grey variants associated with different levels of risk, but it cannot predict with certainty whether an individual pony will develop melanomas.
Are melanomas in grey horses caused by sunlight?
The characteristic melanomas seen in grey horses are strongly associated with grey genetics rather than simply UV exposure.
Are melanomas always dangerous?
No. Many remain small and slow-growing for years. Others enlarge, cause local problems or spread, so changes should not be ignored.
Should every melanoma be removed?
No. Some are monitored while others are treated. Size, position, number, growth and the individual pony all influence the decision.
Can non-grey Connemaras develop melanomas?
Yes. Melanocytic tumours can occur in non-grey horses too, although the strong age-related predisposition is particularly associated with greys.
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