Health Symptoms & Solutions What Are the Most Common Types of Cancer in Dogs?

What Are the Most Common Types of Cancer in Dogs?

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Cancer is one of the most dreaded diseases in the world, for a good reason. Unfortunately, cancer in dogs can be as common as in humans. In fact this is generally true for cancer in pets.

As many experts in veterinary oncology will tell you, early detection can make a huge difference in the outcome or, at the very least, on the quality of life. That’s why it is important for pet owners to understand canine cancers better and to know how to recognize signs of some of the more common cancer.

What Is Cancer in Dogs?

Cancer covers a large number of diseases in dogs. The characterization is the growth of abnormal cells that destroy normal tissue. These cells divide uncontrollably and spread through the body quickly. Some cancers can spread faster than others.

Cancer and the language surrounding it is confusing. Further complications arise when tumors are involved. In short, every cancer is a tumor but not every tumor is cancer.

Some tumors stay in the parts of the body where they have started. These are benign tumors not cancers. Tumors that spread to other parts of the body are called malignant. These are the cancerous ones.

Common Types of Cancer in Dogs

Although the number of cancers that can attack a dog’s body is too high to count, some types of cancer are more common than others.


Lymphoma accounts for 20% of all cancers in dogs, making it the most common type of cancer in dogs. In fact, dogs are more likely to develop lymphoma than humans. This cancer can affect any dog breed and it affects breed dogs of all ages. However, lymphoma affects Golden Retrievers more than other breeds and it more often affects older dogs.

This disease usually appears as swollen lymph nodes in the front of the shoulders, behind the knees or under the jaw. In some cases, lymphoma can occur in lymph nodes in the abdomen or chest and make breathing hard. It can also cause vomiting and diarrhea.

Lymphoma can be treated in most situations but it is dependent on the type. Chemotherapy is the treatment of choice for lymphoma and it has proven quite effective so far. For an in-depth analysis of this specific condition, please read our article dedicated to Lymphoma in dogs.

Woman wears green face mask in operation room. Part of the "What Are the Most Common Types of Cancer in Dogs?" article.
Photo by Artur Tumasjan on Unsplash

Mast Cell Tumors

These tumors usually form on the skin and they can either be relatively benign or exceptionally aggressive in spreading to other body parts. Luckily, skin tumors are most likely to be spotted early since they often appear as lumps and bumps on the skin. That is another reason to brush your dog regularly since you may notice any changes on his skin.

Mast cells are commonly associated with allergies. their official title is cells of the immune system. Dogs that suffer from a mast cell tumor usually show symptoms like diarrhea, vomiting and loss of appetite. Surgery is the preferred treatment for these tumors but in severe cases radiation therapy and chemotherapy are also used. This type of cancer affects Boxers and Bulldogs more than other breeds.


This is a type of bone cancer that affects mostly large and giant breeds like Great Danes, Mastiffs and Irish Wolfhounds. This cancer usually attacks the long bones in the dog’s limbs but it can affect any bone. Unfortunately, osteosarcoma can progress quite fast and spread to other bones, lymph bones and lungs.

Some of the common signs of osteosarcoma in dogs include lameness, swelling and pain in the affected limb. Due to extreme aggressiveness, dogs diagnosed with cancer like osteosarcoma don’t have many treatment options. In fact, they often face the amputation of the affected limb. Chemotherapy for metastases is a common approach.

Sadly, despite these aggressive measures, only around 6% of dogs that undergo the cancer treatment for osteosarcoma live longer than 3 years.


Melanoma is a type of oral cancer that is more prevalent in breeds with dark gums and tongues, such as Doberman Pinschers, Schnauzers, Scottish Terriers and Chow Chows. Proper dental hygiene may help in prevention, although this is only a speculation. At the very least, if you brush your dog’s teeth regularly, you are more likely to notice any changes in his mouth.

This type of cancer is composed of dark cells that can be found anywhere on the dog’s body. Unfortunately, a malignant melanoma will usually spread to the other body parts by the time it is noticed in the oral cavity.

Dogs that develop cancer like melanoma don’t have a good prognosis since this type of cancer is practically incurable. Cancers caught early enough can be eliminated with surgery. Also, veterinary oncologists are encouraged by the effects of immune-based therapies on melanoma.

Mammary Gland Carcinomas

These tumors commonly affect older and unspayed female dogs of all breeds. They can look like small nodules around the dog’s nipples. Sadly, these nodules can quickly turn into large and painful tumors that ulcerate and create an open wound.

About half of the mammary gland tumors are malignant and half of those malignant tumors will become fatal. Cancers can be cured surgically if they don’t metastasize. Additionally, spaying a dog before the first heat cycle can significantly reduce the risk of this cancer.


There exists a direct link between this type of cancer and cells around blood vessels. It usually attacks the spleen but it can also affect the liver, skin and heart. Golden Retrievers, German Shepherds and Skye Terriers are more likely to suffer from this type of cancer than other breeds.

Treating cancer successfully requires early diagnosis. Unfortunately, diagnosis in the early stages is difficult. For example, dogs that suffer from splenic cancers rarely display any signs until the tumor ruptures. When this happens, dogs go into shock and emergency surgery is necessary to stop the blood loss. Chemotherapy is a good starting point although the prognosis is almost always poor.


Cancer in dogs is never an easy thing to deal with. Cancers can’t always be cured but it does depend on the type and size of cancer. If caught early, many cancers can be cured or at the very least the life expectancy can be increased.


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