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Common Signs & Symptoms of Cancer in Dogs

Our Boulder County veterinarians understand how concerning it can be to discover a lump on your dog. While many lumps are not cancerous, several cancers are common in dogs, and it can be beneficial to be on the lookout for signs of this dangerous disease.

Types of Cancer in Dogs

Our dogs are cherished members of our families and are frequently our most devoted friends, so we understand how upsetting it is to think that your dog may be suffering from a serious illness like cancer. While no one wants to think about their dog getting sick, knowing the signs of cancer in dogs and being able to recognize any symptoms early is the best way to help your dog get treatment before the disease progresses.

It may surprise you to learn that dogs can get many of the same types of cancer that people do, and with very similar symptoms.

Here are some of the most common types of cancer that our Boulder County vets see in dogs:


Lymphoma is a very common cancer in dogs, and there are more than 30 different types of lymphoma that can affect them. Lymphoma is a term used by veterinarians to describe a group of cancers that arise from lymphocytes, a type of white blood cell that aids the immune system in fighting infection. Multicentric, alimentary, mediastinal, and extranodal lymphoma are the most common types of dog lymphoma.

Mast Cell Tumor 

Mast cell tumors are skin tumors that can be difficult for your veterinarian to remove depending on their location. The good news is that if the tumor is detected early and completely removed, this type of cancer in dogs can be cured.


Skin tumors are also caused by melanoma. These tumors are frequently found in and around the mouth of dogs, as well as on their feet. Melanoma is a cancerous tumor that spreads quickly to other parts of the dog's body.

Osteosarcoma (Bone Cancer) 

Osteosarcoma is the most common form of bone cancer in dogs. Although any breed can be affected by this type of cancer, our vets most often see osteosarcoma in larger breeds.


This type of cancer is extremely dangerous and necessitates immediate treatment or it will be fatal! Hemangiosarcoma tumors in dogs can grow quite large and are commonly found in the spleen, but they can grow anywhere there are blood vessels and spread to other organs, including the heart and lungs of the dog.


This is a slow-spreading form of cancer in dogs but can be difficult to treat. Amputation and radiation are commonly used to treat dogs with fibrosarcoma, to prevent a recurrence.

Signs & Symptoms of Cancer in Dogs

It can be difficult to spot cancer signs in your dog just by looking at him. Blood tests in dogs frequently fail to detect certain cancers. However, there are some telltale signs that your dog may be suffering from cancer that you should be aware of. When it comes to cancer in dogs, early detection is the key to a successful treatment outcome, just as it is in humans. If your dog is exhibiting any of the symptoms listed below, schedule an appointment with your veterinarian as soon as possible.

  • Sores that don't heal
  • Bleeding or discharge
  • Loss of appetite
  • Unexplained weight loss
  • Strong odor
  • Swelling
  • Lumps or bumps beneath the skin
  • Lethargy, depression, disinterest in exercise
  • Difficult or painful breathing or coughing
  • Straining when going to the bathroom
  • Challenges when eating or swallowing
  • Pain or difficulty walking, lameness or stiffness


While petting and grooming your dog, be aware of any changes in his behavior and pay attention to any bumps or lumps you may feel. Make an appointment with your veterinarian right away if your dog is exhibiting one or more of the symptoms listed above.

Your Boulder County veterinarian may perform a biopsy or other test that will be sent to a lab for analysis, as well as palpate your dog for lumps and bumps. Your veterinarian will be able to tell if your dog has cancer and what the best treatment options are through testing and a thorough examination.

If your dog is showing any of the symptoms listed above or showing other signs of illness contact Lafayette Companion Animal Hospital in Boulder County for help.

New Patients Welcome

Lafayette Companion Animal Hospital is accepting new patients! Our experienced vets are passionate about the health of Boulder County companion animals. Get in touch today to book your pet's first appointment.

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Contact (720) 214-0270