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5 Most Common Cancers in Dogs and Their Symptoms

Jessica Foster | May 17, 2022

According to the Animal Cancer Foundation, 1 in 4 dogs will develop cancer in their lifetime. And while no pet parent wants to imagine their pet fighting this horrible disease, it’s best to get informed about the cancer signs and symptoms early.

Proactivity and education are essential. That’s why we are covering the most common dog cancers and the symptoms to look out for. 

1. Mast Cell Tumours

Mast Cell Tumours are a common type of skin cancer that develops on the skin or just underneath it. Mast cell tumours are quite serious and can cause anaphylactic shock or even death if they are able to metastasize. If you notice a mass on your pet, contact a veterinarian for a professional assessment right away. 

A common treatment for mast cell tumours is a tigilanol tiglate injection to dissolve any non-metastatic mast cell tumours. Surgery may also be used to remove the tumours. 

Common symptoms of mast cell tumours in dogs:

  • Masses
  • Tumours
  • Lesions
  • Swollen lymph nodes
  • Bruises
  • Lethargy
  • Discomfort or pain

2. Melanoma 

Melanomas are another type of tumour commonly found on the skin or mouth but can also be present on the eye or foot. They usually appear as dark-pigmented, round masses between ¼ inch to 2 inches in diameter. The good news is that many melanoma tumours are benign. Still, it's essential to get any unusual bump checked out by a veterinarian as malignant melanomas can be fatal. 

This cancer causes the lymph nodes to swell and can rapidly spread around the dog's body. If that happens, the success rate of treatment drops considerably. These tumours can affect any breed, but Miniature Poodles, Cocker Spaniels, Chows, and Golden Retrievers are most at risk.

Common symptoms of melanoma in dogs:

  • Pigmented spots or blemishes
  • Masses
  • Pain and discomfort
  • Colored bumps around the toenails, mouth, lips or pads of feet
  • Bad breath (oral melanoma)
  • Difficulty eating (oral melanoma)

3. Osteosarcoma (Bone Cancer) 

Osteosarcoma is a common bone cancer in large dogs. Certain breeds like Rottweilers, Great Danes, German Shepherds, and Golden Retrievers are at most risk of developing Osteosarcoma, but any breed can be affected. It can be painful, spreads quickly, and is challenging to treat. So, it's essential to take your pup to the vet if you notice any symptoms like joint pain, swelling, and fatigue.

Common symptoms of bone cancer in dogs:

  • Swelling
  • Lumps
  • Bumps beneath the skin
  • Loss of appetite
  • Weight loss
  • Lethargy

If you notice anything off with your fur baby, book an appointment with your vet ASAP.

4. Lymphoma

Lymphoma is a type of blood cancer that invades the lymph nodes. It causes the lymph nodes to swell and is also commonly seen in the intestines, spleen, liver, and bone marrow. It is very common in dogs, with over 30 different types of canine Lymphoma recorded.

Treatment for lymphoma in dogs is usually chemotherapy.

Common symptoms of lymphoma in dogs:

  • Swelling
  • Masses (abdomen most common)
  • Lack of appetite
  • Lethargy
  • Weight loss
  • Diarrhea
  • Vomiting
  • Breathing problems

5. Fibrosarcoma

Fibrosarcoma is a type of cancer that develops in soft tissue. It is a very aggressive cancer and arises from the abnormal proliferation of cells (fibroblasts). Fibrosarcomas can develop in the bone, limbs, skin, and adjacent tissues.

Fibrosarcomas rarely metastasize but can be locally aggressive. Fast identification and treatment are recommended. The most common treatment includes surgery to remove the tumours, and chemotherapy or radiation. 

Common symptoms of fibrosarcoma in dogs:

  • Pain and sensitivity
  • Tumours
  • General discomfort
  • Lethargy
  • Weight loss
  • Dehydration
  • Lack of appetite or anorexia

Get peace of mind with dog insurance

Your dog is an important part of your life and you do all you can to keep them happy, safe, and healthy. While you can’t prevent every possible ailment, you can get prepared with ongoing care and comprehensive health coverage. 

At Furkin Pet Insurance, we believe your pet deserves access to treatment and healthcare just like we expect for everyone in the household. That’s why we offer dog insurance coverage that helps you get the best care possible should they become sick or injured.

Get help recovering expenses, covering the costs of medications, and more with Furkin Pet Insurance. 

Learn more and get a quote today.


Insurance, M. L. P. (n.d.). 7 most common cancers in dogs. MetLife. Retrieved May 31, 2022, from 

Most common cancers in dogs. Most Common Cancers in Dogs | Cordova Vet | Germantown Parkway Animal Hospital. (n.d.). Retrieved May 31, 2022, from