Cancer has become a lot more common nowadays in both our canine and feline friends. This happens partly because their life expectancy has increased in the past years, with pet parents caring for them better. 

Many pet guardians now do a lot of research with regard to what they are supposed to feed their canine companions to make sure that they benefit from the right nutrition, and the number of cases where pet parents forget to vaccinate their dogs, for example, has decreased significantly. 

However, with a longer life also comes a higher risk of developing cancer. Cancer can be caused by three main things -- environmental factors, genetic predisposition, and actual carcinogenic viruses. 

In this article, we will look at some of the most common types of cancer that can affect dogs. 

1. Mammary Gland Carcinoma

Tumors of the mammary gland are common in dogs and cats alike. Spaying female dogs before they have their first heat cycle can prevent the occurrence of mammary tumors by up to 80%. Unspayed dogs are at a higher risk of developing this type of cancer as there is a hormonal influence on the tissue in the mammary gland. 

Most mammary masses are surgically removed, but biopsy has to be performed in order to determine the exact type of cancer. While some neoplasms can be treated thanks to surgery, there are others that call for other treatment options, including chemotherapy or radiation therapy. 

2. Primary Lung Tumors

Many old dogs develop lung tumors. In most cases, they are diagnosed by accident. If only one tumor is present in one of the lungs, it can be removed surgically. Unfortunately, if the whole lung tissue is scattered with neoplasms, the surgery is not a suitable therapy option. The same goes for cases where the tumor has metastasized. Chemotherapy is recommended in these cases. 

3. Oral Melanoma

Like with other types of oral cancers, oral melanoma mostly affects dogs that have dark-pigmented gums or a dark-pigmented tongue. It is one of the most aggressive types of canine cancer as it usually grows between the bone and the tissue of the oral cavity, making surgical removal difficult, if not impossible.

Since it is so aggressive, most veterinarians remove it as soon as possible, especially if it hasn’t yet affected the bone. Treatment with radiation therapy and chemotherapy is recommended following the surgery. Luckily, nowadays, there is even a DNA-based vaccine available and it offers good results when used on dogs that have oral melanoma.

4. Hemangiosarcoma

Hemangiosarcoma affects the dog’s blood vessels. It is commonly seen in the spleen, the dog’s right heart atrium, and even the dog’s skin. The liver can be a primary site of the disease, but that is not a rule of thumb.

The biggest problem with hemangiosarcoma is that, when it affects the spleen, there are almost zero symptoms that can be seen by the pet parent. This means that the cancer can develop slowly but surely, without the dog receiving any treatment. The spleen tumor can grow to the point that the entire spleen is ruptured, in which case the dog can lose his life. 

When diagnosed early, hemangiosarcoma has a prognosis of 3 to 4 years. 

5. Liposarcoma

Liposarcoma is a malignant tumor of the fatty tissue. It mostly occurs in the axillary region, but there are others that can be developed in the dog’s groin or trunk. Unfortunately, it can also grow inside the pelvic or abdominal cavity or in the chest, in which case an early diagnosis is made difficult due to the absence of any symptoms. 

If the tumor affects the dog’s limbs, it can be removed surgically. Chemotherapy and radiation therapy can be used for treating it, as well. 

6. Osteosarcoma

Bone cancer mostly affects large and giant breeds. It can be commonly found in the limbs. It’s one of the most aggressive cancers that affect our canine friends and it also metastasizes fast and can spread to various parts of the body, including the lungs. 

It’s one of the most painful types of cancer that dogs can suffer from. When it affects just one limb and it hasn’t metastasized, surgical amputation can be a solution. To this date, there are no other effective types of treatment other than removing the tumor itself. 

7. Mast Cell Tumors

Mastocytomas can occur in any organ. In the development of the cancer, the dog’s body immune cells are involved, which is why the location of a mast cell tumor can never be predicted. Skin forms are among the most common ones, but there are others that can affect the urinary or digestive tract, for example. 

Advanced forms of mastocytomas should be treated with chemotherapy and radiation therapy, but there are some types that can be removed surgically. 

Other Common Types of Cancer in Dogs

The seven types of neoplasms that we have showcased here aren’t the only ones that can affect our canine friends. 

Testicular cancer is common in many dogs, especially those that have retained testes. However, most of these cases are preventable with neutering and can be cured with surgery, especially if they are diagnosed early.

Melanoma occurs mostly in dogs that have darker skin. Melanomas are caused by melanocytes, which are effectively in charge of giving skin color. Some of the breeds that are more predisposed to this type of cancer are Standard and Miniature Schnauzers, Doberman Pinschers, Gordon Setters, and Scottish Terriers. Melanoma can be benign and malignant, with the first form usually occurring in areas of haired skin. Malignant melanoma can develop in the distal limbs or the mouth and it is usually incurable. 

Lymphoma is another type of common cancer seen in dogs. It appears as swollen glands under the neck, behind the knee, or in front of the dog’s shoulders. This cancer can occasionally affect lymph nodes that aren’t palpable or visible, such as those in the abdomen or the chest. In this situation, the affected dog can accumulate fluid in the abdomen or chest, which leads to breathing difficulties or digestive problems. Lymphoma is usually treatable, with chemotherapy being the most effective treatment currently available. 

Brain tumors can occur as primary or metastatic tumors. A dog that has a brain tumor typically has epileptic-like seizures or extreme behavioral changes. CAT scanning can determine the exact location of the lesions. Brain tumors can be removed surgically. Those that are inoperable can be controlled with radiation therapy.

Squamous Cell Carcinoma is another type of common cancer seen in dogs. Some of the typical localizations of the tumors are the mouth and the nail beds. With early detection and complete surgical removal, less than 20% of the dogs affected develop metastases. However, if it affects the tongue or the tonsils, it can be quite aggressive, with less than 10% of the dogs surviving for one year, despite receiving proper treatment. 

Bladder cancer is more common in some breeds, such as West Highland Terriers. It is a slow-developing cancer, and unfortunately, most of the dogs that develop it don’t show any symptoms for three to six months. Bleeding and urinary obstruction are the clinical signs noticed by pet parents, in this situation. 

Is Preventing Cancer in Dogs Possible?

Yes and no. Since there are both genetic and viral factors involved, cancer isn’t the most preventable disease. However, since it can also be caused by environmental factors such as exposure to toxins, be they from food or the actual living space where the dog resides, there are some things that you can do.

One of these prevention methods is making sure that you feed your dog a diet as natural as possible. Many veterinarians agree that commercial pet food has lots of artificial colorants and preservatives to make it as cheap as possible. Checking your dog food or cat food ingredients is the right way to go about things. 

Early diagnosis makes a lot of difference when it comes to therapy, and if you want your dog to live a long and healthy life, you should take your pet to the vet on a regular basis. Yearly checkups are required for most dogs that are young and physically healthy, but biannual checkups are recommended for older dogs or those that have chronic diseases. 

Dr. Cristina Vulpe holds a PhD in veterinary oncology. She enjoys writing about animal welfare, nutrition, infectious diseases, parasitology, and a variety of other pet-related topics. She manages a blog about cats, My Feline Buddy. In her spare time, she’s always in the company of a good book and her feline friend.