Cancer In Dogs: Types, Symptoms, Prevention, and Treatment

Cancer is a word that is heard all too often by pet parents. It’s a punch in the gut and it happens all too often. Cancer is responsible for more than half of all pet deaths over the age of 10. This information comes directly from the U.S. Food and Drug Administration (FDA) and nearly matches the rates seen in humans.

Thanks to better treatment advancements, awesome veterinary staff members, and pet parents who are taking the time to get educated on preventions, our beloved pets are living longer. The downside of this is that pets who live longer will have a higher chance of developing cancer.

Sadly, it isn’t just the elderly and the infirm who develop cancer now. Cancer can strike at any age and can take animals who seem to be in relatively good health and suddenly rob them of their vitality and shorten their life.

Is Cancer in Dogs the Same as Cancer in Humans?

Many types of cancer in dogs are the exact same type of cancer that humans also can be diagnosed with. This isn’t true of all species, but it would seem that dogs and humans have this in common. They say that dogs are man’s best friend and we have much in common with them, from emotions to adaptation to our environments, and now … our health.

Types of Cancers in Dogs

  • Hemangiosarcoma - This is a type of cancer that lines the inner walls of blood vessels, forming tumors. This is incurable cancer, often starting in internal organs and spreading into the blood vessels. It most commonly attacks older animals but may also be diagnosed in younger animals on rare occasions. This form of cancer is rarely detected early because of the hidden nature within the blood vessels and it is rare that an animal will live beyond 6 months beyond the original diagnosis.
  • Mast Cell Tumors - These are immune cells that play a key role in allergies. They generally form on the skin of dogs. Breeds such as the Boxer are more susceptible to this type of cancer.
  • Lymphoma - This type of cancer will be found in the lymph nodes of the body, such as in the neck area, under the arms, behind the knee, or near the shoulders. It can cause breathing troubles or possibly show as a chronically upset stomach.
  • Osteosarcoma - This is bone cancer and it amounts to as much as 85% of all the bone cancer cases in dogs that are diagnosed. Large and giant breeds have more of a tendency to be diagnosed with this type of cancer but it can happen to small dogs as well.
  • Brain Tumors - These will typically show the first signs as seizures. Behavioral changes in the extreme may also be a symptom that is noticed first. A CAT scan or an MRI will help make the diagnosis. If it is an operable tumor, it may be removed or it could be treated by chemotherapy only.
  • Bladder Cancer - This form of cancer is slow-progressing and often shows the first symptoms after three months. Generally, the first symptoms may be bleeding during urination or complete blockage of the urinary tract.
  • Mammary Carcinoma - If caught early, this form is operable and involves removing the mammary gland. If it has spread (metastasized) it will only be able to be treated with chemotherapy and the survival rate is slim. Female dogs who have not been spayed are most at risk.
  • Malignant Histiocytosis - This form of cancer is rarely treatable. It may involve one or more organs as it spreads. It will form lesions on internal organs and will break their tissues down and destroy them. No treatment has ever proven effective for this type of cancer. Sporting breed dogs seem most likely to develop this form of cancer.
  • Squamous Cell Carcinomas - This cancer tends to form in the mouth and in the nail beds. Surgical removal is the best option unless the cancer has spread to tonsils or down the throat. Fewer than 10% of dogs tend to survive beyond one year if cancer has metastasized.
  • Mouth and Nose Cancer - Common symptoms are bleeding from the nose or mouth, bad breath odor, swelling in the facial or nasal area. Early treatment is essential in this very aggressive form of cancer that is also one of the most common cancers in dogs.
  • Melanoma - Melanomas sadly happen most often in dark-colored dogs, making it difficult to see them until it is too late. This form of cancer spreads rapidly and will be inoperable by the time it is detected, most of the time.
  • Testicular - Removal of the testes immediately will often cure this cancer if it has not spread. Neutering early in life prevents this cancer from ever forming. 

If these cancers sound familiar, it is likely because you’ve heard them diagnosed in humans as well. The treatments are available for dogs that also are used to treat humans too. The issue is that most people don’t have insurance in place to cover the cost of the treatment for their pets in many cases.

Are There Different Types of Cancer Dogs Can Get?

There are types of cancer that are specific to dogs. Hemangiosarcoma mentioned above, is exclusive to dogs, cats, and horses. This form of cancer is not seen in humans. 

Dogs also get Transmissible Venerable Tumours (TVTs) and they are very different from human forms of cancer in that they can be spread to other dogs via sexual contact or from licking at the sight of a tumor. Dogs can ingest cancerous cells and become infected with this form of cancer themselves.

Luckily, TVTs are more frequently seen in the tropics and the subtropical areas of South America, Asia, and Africa, but it is possible in the Southern United States. This type of tumor is hard to detect and made more difficult depending on the exact location. A penis lesion may cause a thickening or hardening of tissue but isn’t always visible, for example.

Watch your dog for signs of constant licking which can be a symptom. A biopsy will be necessary to determine the presence of this cancer and if it is diagnosed, surgical removal of the cells is the best treatment. This form of cancer rarely spreads.

Terms to Know

  • Neoplasia - This refers to a new growth of tissue that isn’t considered normal. A large mole, for example, that grows very quickly with an irregular shape.
  • Tumors - A swelling that is formed from abnormal growth of cells, forming a tissue that will not generally be inflamed as we normally would think of swelling.
  • Malignant vs Benign - Malignant growths, or tumors, are cancerous. Benign tumors are those that have been tested and determined to be free of cancer.
  • Biopsy - Removing some cells for testing, cytology, to see if cancer is present.
  • Carcinoma - Cancer that begins on the skin or on the surface of a body organ.
  • Oncology - The treatment process for cancer. Oncologists are physicians who specialize in cancer treatment.
  • Metastasis - Cancer that has spread to other organs or parts of the body.
  • Sarcoma - Type of cancer that starts in the bones, cartilage or blood vessels. It may be in connective tissues of the body, including fat.
  • Tumor - An atypical mass of cells that have formed. It could be cancerous or not, ie malignant or benign. 

These are not all of the terms you may encounter with cancer and the treatment thereof but these represent the more common terms when speaking with your veterinarian about your pet’s diagnosis.

Common Causes of Cancer in Dogs

Many people would like to know what the cause of their pet’s cancer is for a myriad of reasons. Sometimes we just want to make sure it wasn’t something we did or could have avoided. The hard truth is that most cancers are a combination of genetics and the environment.

Prolonged exposure to water with lead in it is going to cause issues for a pet, a human, any living creature. That would be a case of environmental influence. Genetics is simply what they’ve inherited from parents, grandparents, and their entire family tree.

Good breeders will not breed from dogs that have a family tree with cancer in it. This helps ensure that the genes are not passed on to more animals. Sadly, many people breed dogs without ever having them tested for cancer or the risk factors that may indicate they have a strong tendency toward this in their genetics. 

The main thing you should remember is not to beat yourself up. There’s rarely anything you’ve done or could have known about that would have caused your pet’s cancer. Focus your energy on the treatment and making them comfortable once they’ve been diagnosed. You’ll find this is a better way to use your time and energy. They will have good days and bad days until they begin having more bad days than good days.

How Do I Choose a Treatment For My Dog?

  • Consult with your veterinarian - Your pet’s doctor is the main person to talk to and ask questions of. They are trained to treat pets for cancer, receive ongoing training in new technologies and advancements in medications, and they know the statistics to give you a prognosis that is somewhat dependable. Some pets will beat the odds, but your veterinarian can give the blunt truth to be your starting point.
  • Costs/Insurance - Mentioned much earlier on, many pet owners find themselves in the predicament of having no insurance for cancer treatment for their pet. It simply isn’t as common as health insurance for humans is but it is making a surge. If you’re a pet owner, get insurance before there is a medical need. Cancer treatment can cost many thousands of dollars. Don’t let that be what stands in the way of treating your friend who has been loyal and loving.
  • Know when you have reached the point of making them comfortable - This is very hard to come to terms with. This is also the point at which we all question ourselves. Will I know when it is time to end his suffering? Work with your veterinarian and be ready to accept when they feel that it is time to do what is most humane for your pet. We don’t want them to suffer. We have the ability to release them from their pain and anguish and when they stop eating and drinking, can no longer stand, and their bad days are far more common than their good days, the time has come to release them. Your veterinarian can humanely end their pain.

The end of life care is the most difficult time because we are acknowledging that there is no longer any hope. Treatment options have been exhausted and the priority is now to make our pet as comfortable as possible and help them to live the best life they can until life is too hard for them. We struggle emotionally at this time and for many parents of beloved family pets, the decision is gut-wrenching. 

Your veterinarian and staff are there for you. Lean on them to help make the decisions when you emotionally are not able. Understand that they are also sad because they’ve treated your pet for a long time and you are all grieving together. Most veterinarians will not show their sadness, but they do feel it and cry at night when the doors are locked behind the last patient.

Ten Steps to Take When Dogs Have Cancer

  1. Acknowledge that your pet has cancer and focus on what to do, don’t wallow.This is really important to attitude and his/her quality of life in the end as well. 
  2. Learn all you can about the form of cancer they’ve been diagnosed with. Understanding what to expect helps you deal with it as it comes. 
  3. Know the treatment options and all the implications of them. Find out all about the ways your veterinarian can treat them for pain, nausea, and other complications that can come from treatment also. This is huge. Be prepared for side-effects and repercussions of treatments. 
  4. Find an oncologist that specializes in pets. These doctors are amazing and what they’ve seen and learned can help guide you in your decisions in what will be an emotional journey. A good oncologist can make all the difference in the world. 
  5. Read everything you can find and learn the lingo. No matter how great your doctors are, you will feel empowered when you have a clear understanding of what is happening. The more you know, the better your decisions can and will be. 
  6. Understand the testing and how the diagnosis is made. Know how tumors are tested and what happens at this point when a diagnosis is made. Understand the stages of cancer and expectations.
  7. Make your pet’s quality of life the single, most important factor. Cancer is not always curable. Typically, the goal is extending the life of your pet. Many pets might live another year, two years, even as much as five years longer. As long as their quality of life is good, you should want to do all you can to extend their life. 
  8. Consider the financial obligations and be realistic. You are likely not in a position to throw hundreds of thousands of dollars into cancer care. Most families are forced to decide that they have a cap on their spending for treatment. Knowing this ahead of time, before you reach your limit, will help you to make the best decisions along the way. 
  9. Try to continue with your pet’s daily activities and routines until he just no longer can. Keep your lives as normal as possible. Your pet will appreciate being able to enjoy the time they have left and you’ll be glad you spent that time with them too. 
  10. Have the audacity to hope. There is always hope. Don’t give up on him/her. There is always hope and that is what keeps us all going. Remember, your pet doesn’t know he has cancer. He has no idea that his time may be limited and he will give you his all until he can no more.

Your dog isn’t going to give up easily. The heart of a dog simply doesn’t know how to quit and they will fight. Be strong for them, stand by them, and focus on one day at a time. Cancer isn’t always a steady decline and there can be remissions in certain forms of cancer.

Having a pet diagnosed with cancer doesn’t have to be a death sentence. It also doesn’t mean that you’re going to lose your pet soon. Much depends on the form of cancer and what stage it is in. Keep a cool head and make informed decisions. Let your pet be your guide. He’ll let you know what it is time to say goodbye and until that time comes, enjoy them and give them the best days that you possibly can. All they know is today. Make it great.


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