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Cancer is one of the leading causes of death in dogs, especially for those of significant age. In this guide, our friends from Noble Vet Clinics will talk about the 12 common signs of cancer in dogs. Once you know what to look for, you’ll be ready.
With that, let’s start by learning what cancer actually is.
What Is Cancer in Dogs?
Cancer occurs when abnormal cells begin to grow in a dog’s body. These cells can create tumors, which can be benign or malignant. While benign tumors are harmless, malignant ones are aggressive and can invade nearby tissues.
This condition can affect virtually any part of the body. Some of the most common types of cancer in dogs include:
- Lymphoma. A cancer that originates in the lymphatic system, affecting the spleen, lymph nodes, and gastrointestinal tract.
- Mast Cell Tumors. Skin tumors that develop from mast cells, a type of white blood cell involved in a dog’s immune responses.
- Osteosarcoma. A type of bone cancer in dogs common in large and giant dog breeds. Osteosarcoma is often painful and aggressive.
- Hemangiosarcoma. This is a highly aggressive cancer that starts in the blood vessels and is common in large and older dog breeds.
Common Signs of Cancer in Dogs
While some cancers develop slowly, others progress rapidly, and they can show the most subtle of signs. These include:
1. Lumps and Bumps
The presence of lumps and bumps can be a key indicator of canine cancer. These growths can develop suddenly, feel unusually firm, or have irregular shapes. Many owners first notice them while petting their dog and coming across a hard mass that wasn’t there before.
Common cancers that exhibit lumps include:
- Mast cell tumors
- Mammary gland tumors
- Soft tissue sarcomas
2. Weight Loss
Weight loss can be one of the first signs of an internal problem. It often shows up before anything else. Affected dogs can have more visible ribs, hips, or spine, without enough muscle to conceal them.
Common cancers linked to weight loss include:
- Lymphoma
- Liver cancer
- Gastrointestinal tumors
3. Reduced Appetite and Difficulty Eating
Another common sign of cancer in dogs is a reduced appetite, which often leads to weight loss. You can see this when they sniff their food then walk away, ignore treats, and skip their meals.
Additionally, some cancerous growths can also make it hard for dogs to eat, which even furthers their loss of appetite.
Some of the cancers that lead to a decreased appetite include:
- Stomach cancer
- Liver cancer
- Oral tumors
4. Non-Healing Sores
Sores look like small wounds or scabs that just won’t go away. They may have bleeding or discharge and seem to keep reopening even after treatment. While occasional cuts or scrapes are normal, sores that linger on for weeks could be a key sign of cancer in dogs.
Sores are commonly found in cancers such as:
- Squamous cell carcinoma
- Mast cell tumors
- Cutaneous lymphoma
5. Foul Odor
In some instances, a persistent, foul odor can be a sign of cancer in dogs. This scent can come from their ears, mouth, skin, or rear ends, areas where tumors can potentially grow. They can also indicate ulcerated tumors. Cancer-related odors usually stem from dying tissue, bacterial buildup, or internal bleeding.
Some of the cancers in dogs that present a foul odor include:
- Oral tumors
- Anal sac tumors
- Nasal tumors
6. Bleeding or Discharge
Bleeding or unusual discharge generally indicates trauma or infection, but can also mean a tumor affecting an internal organ or mucous membrane. You might notice blood in your dog’s urine, stool, saliva, or nasal discharge.
In other cases, there may be pus-like discharge from the eyes, nose, ears, or genitals. Cancers that generally exhibit bleeding and discharge symptoms include:
- Hemangiosarcoma
- Nasal tumors
- Bladder cancer
7. Difficulty Breathing
Tumors that grow within a dog’s airways can cause obstruction and respiratory problems such as persistent coughing and labored breathing. Affected dogs may take shallow breaths, wheeze, or not have the energy to do anything at all.
Cancers that cause breathing problems include:
- Lung cancer
- Lymphoma
- Tracheal tumors
8. Reluctance to Exercise and Play
Tumors affecting vital organs, muscles, or the cardiovascular system can cause fatigue, leading to a reluctance to play or even move at all. Affected dogs may hesitate to climb stairs, walk to their owners, or get up.
Common cancers with this symptom include:
- Lung cancer
- Osteosarcoma
- Heart tumors
9. Persistent Lameness or Stiffness
While stiffness is generally caused by arthritis, persistent lameness can also be caused by cancers that affect a dog’s mobility. These growths are generally found in the parts dogs use for moving. In some cases, affected dogs can suffer fractures due to the weakened bones.
Cancers include:
- Osteosarcoma
- Soft tissue sarcomas
- Fibrosarcoma
10. Abdominal Swelling or Distension
A swollen abdomen can indicate fluid buildup, internal bleeding, or the presence of abnormal growths, all of which can be caused by cancer. This symptom often suggests a tumor on the spleen, liver, or gastrointestinal tract.
Common cancers in dogs with this symptom include:
- Hemangiosarcoma
- Liver cancer
- Intestinal tumors
11. Straining to Urinate or Defecate
Tumors that grow on a dog’s urinary tract and rear end can make urinating and defecating difficult. You can notice this when your dog takes a long time to pee, has indoor accidents, or tries to urinate without any success.
Cancers that present this symptom include:
- Prostate cancer
- Bladder cancer
- Urinary tract tumors
12. Neurological Changes
Tumors affecting the nervous system often result in far more severe changes. Dogs may become unusually aggressive, withdrawn, or confused. In more advanced cases, neurological cancers can trigger seizures, head tilts, and loss of balance.
Cancers with these symptoms include:
- Primary brain tumors
- Secondary brain tumors
- Spinal cord tumors
Conclusion
Cancer is one of the most challenging conditions dogs and their owners can face. But the earlier we catch the signs, the better the outcome. With knowledge of some of the most common signs of cancer in dogs, you can give your best friend a fighting chance.