Mammary Tumors in Dogs
Can come in several different forms with half of them benign and the other half cancerous

Mammary tumors in dogs are the most common cancer in females, and if your dog develops this potential killer, they have a 50 percent chance of it becoming malignant.

Once it does become malignant and spreads, your dog may have very little chance of surviving this very dangerous form of cancer.

While the exact cause of mammary tumors is not fully understood by the medical community, there is one fact that is fully understood.

The risk of this cancer is almost entirely eliminated if they are spayed before their first heat.


Mammary tumors in dogs are very similar to breast cancer in women, and they can be every bit as lethal.

The exact cause of this form of cancer is not fully understood, but it is widely held that hormones play what is considered to be an elusive role.

Beagle dogsMammary tumors in dogs first symptoms can be very scary

These include Estrogen and progesterone, and these tumors can occur in intact, or non-neutered dogs, as well as spayed dogs.

However, it is much more common in non-sprayed middle aged females.

The average age that a dog contracts this form of cancer is between five and ten, although in rare cases it has been found in female dogs as young as two years old.

But there is one slight misconception about mammary tumors; they do not only affect females.

Male dogs can also be attacked by this cancer, although it is not nearly as common.

If it does affect a male, it is considered to be an extremely dangerous condition as it is usually very aggressive and most male dogs will not survive it.

It is also widely held by the medical community, that if you have your dog spayed, it dramatically reduces the chances of them developing mammary tumors.

In fact, if female dogs are spayed prior to their first heat cycle, it is estimated that they have less than one percent probability of developing this cancer.

Once they pass their first heat cycle, it is estimated that they now have about an eight to ten percent chance of developing it.

If you wait until the second cycle, their probability of contracting it jumps to twenty five percent.

It is a theory, and it must be stressed, just a theory, that by eliminating or reducing the two hormonal factors dramatically reduces your dog chances of developing this very dangerous cancer.

However, the numbers seem to support this theory.

It is also held that there may be other hormones that factor into this equation other than just estrogen or progesterone, although that has never been documented.

Mammary tumors in dogs can affect all breeds, but there are some that seem more predisposed than others.

The breeds that are affected the most by mammary tumors in dogs include Poodles, Cocker Spaniels, and all of the Terrier breeds.

However, German Shepherds are also included in the higher risk grouping.

There is one other factor that has also been suggested; weight. It is also believed that the heavier a dog is the better chances they have of developing this cancer.


Mammary tumors in dogs come in several different forms. However, it is very important to note that fifty percent of all cases are considered benign tumors, and the other fifty percent is malignant.

Once your veterinarian has identified which type of growth it is, it will help them to zero in on the applicable form of treatment.

If the tumor is benign, the tumor is considered to be a mixture of several different types of cells that are found in your dog.

This is perhaps one of the reasons that it has been so difficult for the actual cause to be identified.

It is very rare in most species, including dogs, for a single cell tumor to actually possess more than one kind of cancerous cell.

This form of combination cancer in dogs is referred to as benign mixed mammary tumor, as it contains both glandular as well as connective tissues.

Other benign tumors that can cause these particular growths may include fibroadenomas, simple adenomas, as well as complex adenomas.

There are also several malignant mammary tumors in dogs and they include tubular adenocarcinomas, solid carcinomas and anaplastic carcinomas.

Malignant mixed tumors is another possibility. 


Mammary tumors in dogs will show you several symptoms, and most of them will be both very apparent as well as frightening.

Mammary tumors will first surface in one of two fashions; as a single mass swelling or multiple swellings.

When they do surface, they will be very easy to detect as they appear as a gentle palpating that is occurring in the mammary glands.

If you see this happening, gently touch them. If they feel like small gravel, all of your warning signals should go off.

They are usually very hard and if they are, do the next test which is trying to move them, but very gently. If they do not move at all, this is even more of a confirmation.

Most all dogs have five mammary glands, and each of these glands will have a nipple that are located on both the right and left side of their lower abdomen.

This form of cancer can affect all five of these glands, but it usually affects the fourth and fifth gland.

If you were to image a number sequence on your dog looking at them as they are standing, the first gland is located right below their front shoulder, but of course on their abdomen.

However, this will help to paint a picture in your mind of where they are located.

This number sequence will continue one thru five, with five being located right above their rear legs, but on their belly.

Check the fourth and fifth glands first. This helps to identify this potential killer much easier in the initial stages. Once you have identified them, watch very closely for the next symptoms.

In most every case of mammary tumors, there will be more than one growth that you will observe.

Although it may be very difficult for an owner to identify what type of tumor it is, there are some very helpful methods.

Benign tumors are in most every case very smooth as well as very small, almost like a pea.

They will also grow very slowly. Conversely, malignant tumors are almost the complete opposite.

They will have very irregular shapes, are very firm, and they grow extremely fast.

There are also several other symptoms and early warning signs to watch for with mammary tumors in dogs.

The next set of signs is bruising of your dog’s skin directly over these growths, as well as ulcerations or open wounds on the mammary glands themselves.

If your dog starts to bleed anywhere on their skin, this is also a real warning sign.

However, if these warning signs are not enough to frighten you, the next two will; a difficulty in breathing as well as coughing.

Coughing will usually precede the difficulty in breathing, and is the most dangerous warning sound you will ever hear your dog make.

Your dog may cough briefly if they have eaten or drank too fast, but this will be a sudden and persistent cough for no apparent reason.

You know you know the reason; they are signaling you that something is very wrong.


Mammary tumors in dogs are a life threatening disease, but if it is caught in the early stages, there are several very effective treatments.

However, you can dramatically reduce the chances of your dog ever having this potential killer by having them spayed before their first heat.

Spaying has several other advantages including controlling the population, but it this case it may save your dog’s life.

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