Types of Tumors in Dogs

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Just like people, dogs can develop tumors as well. Tumors can go by many handles, depending on the vet and the day. Some call them growths, some call them masses, others call them tumors or abnormal tissue.

However, these terms are general, and are usually not a cause for panic. The mass has to be properly tested to determine whether or not it is benign or malignant, and to determine the type of tumor it might be. Only once it’s been properly tested and deemed malignant should you be overly concerned.

Often, it’s when you are petting or grooming your dog that abnormal growths are even found. Many times, they may be virtually unnoticeable, which is why it’s important for you to see your vet regularly, and to give your dog wellness exams. At a wellness exam, your vet will perform a thorough physical exam, and will find things that you yourself may not find.

That said, here is a review of several common types of tumors and growths found on dogs, ranging from benign to malignant.

Cysts

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Sometimes dogs simply develop cysts on their body, which are filled with fluid. Cysts can pop up just about anywhere, and are usually either on or just beneath your dog’s skin. Most cysts are benign; however, it is always better to be safe than sorry. Have your vet check it out to confirm that it’s not malignant, if only to ease your mind.

If it is benign, unless the cyst is bothersome for your dog, they will probably leave it alone. If it is bothersome, it can be drained, although it will usually fill back up again at some point. Surgery is sometimes an option, but of course, that will be up to you and your vet.

Sebaceous Cyst

This is a common benign cyst that is filled with something called sebum. Sebum is the oily stuff that is usually thick and found around a dog’s hair follicle. Sebaceous cysts can occur anywhere, and should not be squeezed or “popped” as it can lead to irritation or skin infections in dogs. While this type of cyst is not malignant, it can be mistaken for sebaceous gland adenocarcinoma, which is malignant. If you aren’t sure, have your vet run tests.

Lipoma

Lipomas are benign skin tumors made up of excess fatty tissue. They can range in size, and surgery isn’t typically recommended for this type of tumor unless its growth hinders your dog’s ability to move around and be active.

Lipomas tend to grow beneath the skin along the groin, the trunk, and the limbs. Sometimes these tumors can grow internally, inside the chest or abdomen, and cause discomfort by pressing in against the organs. There is also a malignant form of lipoma, that is called liposarcoma, but your vet would have to perform a biopsy to discern the difference. Lipoma tumors are common to many dog breeds.

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Papilloma

This is another benign tumor type, which essentially refers to dog warts. Unfortunately, these types of tumors can cause quite a bit of problems despite their benign status. They resemble cauliflower in appearance, and tend to appear on the lips and around the eyes, as well as inside the mouth.

When these growths appear, they can be painful and infectious, and cause significant difficulty with chewing and swallowing. This type of tumor is caused by a virus called the papillomavirus, and it can be passed around through other dogs or objects that have been contaminated.

Unfortunately, this type of virus can incubate for months at a time, so by the time you see symptoms manifesting in your dog, it could have already spread to other dogs in your household as well. Papilloma tumors usually go away on their own within a few weeks to a couple months. If they don’t, or if they cause major discomfort, you may have to see your vet and request to have them removed.

Histiocytoma

Histiocytoma is a tumor that occurs most often in dogs younger than three years, and in particular breeds, such as the Scottish Terrier, Boxer, Boston Terrier, Greyhound, English Bulldog, and Chinese Shar Pei. This tumor develops via the immune system, and is usually benign and resolves on its own.

Unless the tumor is causing your dog some kind of discomfort, surgical removal probably won’t be recommended. This type of tumor is often small, causing a red, hairless, raised little lump that looks a bit like a button. They are sometimes called “button tumors” for that reason.

Mast Cell Tumors

Mast cell tumors are extremely common in dogs. It is possible it is the most common type of tumor found in dogs. Mast cells are immune cells that relate to the allergic response. Because they are found throughout the body, this type of tumor can develop virtually anywhere.

However, they most often develop on the skin, and sometimes in the urinary and digestive tracts. Prognosis is less positive when the tumors develop in the urinary and digestive tracts, whereas tumors in the skin offer a more positive outlook.

Mast cell tumors are fast-growing, and will typically manifest as red and itchy. They itch because the lumps contain the chemical histamine, along with serotonin. Histamine is the same chemical that causes itching with allergies, and the two chemicals combined, when running through your dog’s bloodstream in large quantities, can cause additional unpleasant symptoms. These include vomiting and diarrhea as well as a loss of appetite in dogs.

It is worth noting that breeds with short faces, such as Pugs, Boxers, and French Bulldogs appear to have the highest risk for developing this type of tumor.

Osteosarcoma

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This type of tumor in canines is a common form of bone cancer. It typically affects giant and large breed dogs, such as Great Danes as well as Greyhound. If your dog has osteosarcoma, his legs could be affected, and you may notice him limping.

Sometimes, bones in the spine can be affected as well. This type of tumor can spread from your dog’s bones throughout his body, including to other bones as well as the lymph nodes and the lungs.

Amputation is often necessary, because this type of disease is painful for your dog. Amputation combined with chemotherapy can slow down the spread of the disease, and give your dog an extra year or two of life.

Hemangiosarcoma

This type of tumor affects cells that line the blood vessels along the skin, the spleen, and the right atrium of the heart. The spleen seems to be most common, due to its large blood supply. This type of tumor can affect the liver as well. Sometimes, a dog with tumors on the spleen will show no clinical warning signs, until the tumor ruptures.

When this happens, your dog needs to see the vet immediately to stem any internal bleeding, and to remove the spleen. Chemotherapy will most likely be recommended to stop metastasis. The prognosis for hemangiosarcoma in dogs can be a few months to several years, depending on where the primary tumor is located. This type of tumor tends to afflict larger breeds such as German Shepherds and Golden Retrievers.

Anal Gland Adenocarcinoma

If you’ve ever taken your dog to a groomer, you know that your dog has a pair of anal glands that usually need to be drained. These glands house a liquid substance with a strong odor, one that is typically released while defecating.

Although tumors in these glands aren’t common, they do occur, and when they do, they can be quite aggressive. This is why a regular wellness exam with your vet is very important, to detect illnesses like this early on.

Unfortunately, this type of tumor can spread through the lymph nodes throughout the rest of the body, so early detection is vital. Then, if possible, removal by surgery is the best course of action. Typically, dogs with smaller tumors have a better prognosis than dogs with larger tumors, although it’s not known why.

Lymphoma

Lymphoma is a cancer of the blood, involving a white blood cell called a lymphocyte. The most common manifestation of this type of cancer is a tumor of the lymph nodes. Sometimes this tumor may appear on the skin, or infect the gastrointestinal system and nervous system. The good news is that this type of canine cancer is highly treatable, with a good overall prognosis.

The most common course of treatment for dogs with lymphoma is chemotherapy. When inspecting your dog, the places where swelling may be the most noticeable is under your dog’s jaw, as well as behind the knees and along the front of the shoulders. As to breeds, this type of tumor can affect all breeds, it doesn’t discriminate.

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Melanoma

Melanoma is a type of cancer that related to pigmentation cells. These tumors will usually be dark brown or black in color. Often, these tumors can be benign, except in the case of tumors that are in the mouth or in the bed of the nail.

If a tumor affects the nail bed, amputation may be recommended to remove the cancerous tissue entirely. This type of cancer can also metastasize to other parts of the body, such as your dog’s lymph nodes and internal organs. This is why amputation is recommended, to offer the best chance at recovery.

Unfortunately, just like with people, chemotherapy is not an effective treatment for melanoma in dogs. However, surgery combined with immuno and radiation therapy can be. In the case of oral melanoma, removing the tumors completely can be tough, so you will need to find an experienced veterinary surgeon to assist you in your dog’s care for the most positive prognosis.

Thyroid Carcinoma

This is a type of tumor that is more likely to affect older dogs. Lumps will often appear on a dog’s neck, and you might feel it as you pet them. Depending on the tumor, it could emit the thyroid hormone, and cause  hyperthyroidism in your dog.

Signs of hyperthyroidism include panting, hyperactivity, weight loss, and an upset tummy. Dogs that don’t display any hyperthyroid symptoms, but still test with high thyroid hormone levels, need to be examined for signs of a tumor.

If a tumor is found, the best course of action is to remove the growth with surgery, and radiate any remaining parts of the mass. Sometimes, chemo is recommended so that the tumor doesn’t metastasize and spread elsewhere in your dog’s body.

Squamous Cell Carcinoma

This is a tumor that can pop up on the skin, or in the mouth, and typically look asymmetrical and “raw”. These tumors are usually pink or reddish in color, and are thought to be caused by sun exposure. Sometimes it’s called oral squamous cell carcinoma, and is found along the gums and in the tonsils.

This type of tumor in dogs can also spread to other parts of the body, including your dog’s bones. However, if it’s the skin type, it doesn’t usually spread and stays localized to the place where it is found.

The skin squamous cell carcinoma is actually quite rare, and when it does appear, it is often around a dog’s nail beds. Surgery is typically the preferred treatment, and chemo may be recommended if surgery isn’t completely successful.

Mammary Gland Carcinoma

Mammary gland tumors are another common type of tumor in dogs, especially in female dogs that have not been spayed. Hormones interact with the mammary tissue, and when that happens, tumors can develop.

There is typically a 50/50 chance that the tumor a dog develops will be cancerous, and a 50/50 survival rate in dogs diagnosed with a cancerous tumor. Surgery as a treatment option is usually sufficient, however, in some cases a vet might recommend chemo too, as a way to prevent metastasizing or returning.

Anytime that your female dog show signs of an inflammation of the mammary gland, she should be seen by a vet immediately. An inflamed mammary gland is called mastitis, but if your dog has a tumor, it can also cause inflammation, so testing needs to be done to rule out one or the other.

It’s worth noting that a malignant mammary gland tumor is more likely to be found in a female dog that has not yet been spayed, than in female dogs that have been spayed. This is one of the reasons why pet owners are often urged to spay their females if they do not intend to breed them.

As you can see, there are many types of tumors in dogs, with some of them being scarier and more aggressive than others. If you find a suspicious lump or mass on your dog, try not to freak out about it. It could very well be benign, and you won’t know that until you see your vet and get a proper biopsy and diagnosis.

So, if you find a growth, take a breath, take things one step at a time, and make an appointment with your vet. From there you can decide if a biopsy and further testing is in order, and what, if any specialized treatment options your dog may need. Tumors in dogs can be worrisome, but in many cases, they turn out to be no big deal at all.

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