Cancer in Dogs: Common Signs and Symptoms

We know that finding a lump on your canine friend can be very worrying, especially since there are several common cancers in dogs. Our San Diego vets help you understand the symptoms and signs of cancer in dogs.

Types of Cancer in Dogs

Our dogs are much-loved members of our families and are frequently our most loyal of friends, so we know that it's distressing to think that your dog may have an illness as serious as cancer. Knowing the symptoms and signs of cancer in dogs can be crucial to spotting the disease before it becomes more advanced.

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 College Animal Hospital vets see in dogs:

Mast Cell Tumor

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

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 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.
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 form of cancer is very serious and requires emergency intervention or it may be quickly fatal! Hemangiosarcoma tumors in dogs can grow quite large and are often found in the spleen, but may grow anywhere blood vessels are present and can spread to other organs, including the dog's heart and lungs.


Melanoma also causes skin tumors. These tumors will often be found in and around the dog's mouth or on the dog's feet. Melanoma is prone to spreading quickly to other areas of the dog's body and tends to be malignant.


Lymphoma is a very common form of cancer in dogs and there are more than 30 types of lymphoma that dogs can develop. Lymphoma is a generic term used by vets to describe a group of cancers that stem from a type of white blood cell called lymphocytes that help the immune system fight off infection. The most common types of dog lymphoma are multicentric, alimentary, mediastinal, and extranodal lymphoma.

Signs & Symptoms of Cancer in Dogs

It can be difficult to detect signs of cancer by simply looking at your dog. Even blood work often cannot detect certain cancers in dogs. That said, there are some signs that you can watch for that can indicate your dog may have cancer. As with people, early detection is the key to positive treatment outcomes when it comes to cancer in dogs. If your dog is displaying any of the following signs, make an appointment to see your vet as soon as possible.

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


It is essential to be aware of any changes in your dog's behavior and pay attention to any bumps, lumps, or abnormalities you may feel while petting and grooming your dog. If your canine friend is displaying one or more of the symptoms listed above, make an appointment to see your vet immediately.

Your College Animal Hospital vet may perform a biopsy or other test that will be sent to a lab for testing, as well as palpate your dog to feel for any lumps or bumps. Through testing and a thorough examination, your vet will be able to determine if your dog has cancer and what the best treatment options are.

If your dog is showing any of the symptoms listed above or other signs of illness, contact our San Diego vets to schedule an appointment.