However, it’s a condition that is usually difficult to detect, especially in its early stages. Plus, the common symptoms of cancer in dogs​ often resemble generic diseases and even relatively harmless conditions. 

Still, it’s important to take note of the possible signs so you can get your dogs the help they deserve.

What Is Cancer in Dogs?

In essence, cancer is a group of diseases that stem from abnormal cell growth. Normally, the body’s cells grow, divide, and die in a regulated cycle. But in cancer, these cells begin to multiply uncontrollably, disrupting this process. 

From here, these abnormal cells can either form benign or malignant tumors. 

In dogs, tumors can grow in any part of the body, from the skin to the organs within. Different types behave in many different ways. 

How Do Dogs Get Cancer?

Canine cancer happens due to several reasons, namely genetic, age, environmental, and lifestyle factors. Because of its genetic factor, some dogs carry an increased risk of cancer, which includes:

• Golden Retrievers

• German Shepherd

• Rottweilers

• Poodles

• Great Danes

• Beagles

• Saint Bernards

Additionally, cancers in dogs can be caused by their age. Since the abnormal cells do take time to grow, they are often common in older dogs. This is because their immune systems weaken, their cells accumulate more DNA damage, and they experience increased cell division. 

Environmental factors also play a role in increasing the risk of cancer, especially carcinogens. These chemicals are cancer-causing substances that can damage a dog’s DNA and stimulate tumor growth. 

Carcinogens are common in a dog’s environment, especially in urban settings. Other common environmental factors include:

• Secondhand smoke

• Pesticides

• Industrial pollutants and toxins

• Excessive UV exposure

• Poor air quality

At What Age Do Most Dogs Get Cancer?

Generally, the risk of cancer increases with age. This means dogs can get cancer as they get older, at the age of 8.8, as the median age for diagnosed cases. 

However, the risk still increases based on the dog’s genetics and environment. So, if a dog is prone to having cancer, they can get it at an age younger than 8.8.

How to Tell if Your Dog Has Cancer​?

Each type of cancer has its own set of signs, some of which are shared across different types. Here are the common symptoms of cancer in dogs:

1. Unexplained Lumps or Bumps

One way to tell if your dog has cancer is by checking for abnormal growths. You might see or feel lumps on your dog’s skin. It can be soft or firm, small or large. These growths can stay for months or grow rapidly. In some cases, they can ulcerate.

While not all growths are cancerous, they should still be checked. Depending on the location of these masses, they can cause significant discomfort for your dog. 

Common cancers with this sign include:

• Mast Cell Tumors. These lumps can be found on the skin as a noticeable growth or swollen mass. They often look like pimples. 

• Soft Tissue Sarcomas. STS can develop lumps on areas where soft tissue is present, such as the limbs, chest, and back. 

• Mammary Gland Tumors. These lumps can be found on the mammary chain of affected dogs, appearing as red masses. 

2. Lameness and Limping

If your dog starts limping or having difficulty moving, then it can also be a potential sign of canine cancer. Some dogs also tend to hesitate and choose not to get up and walk at all. 

While it can be thought of as a sprain, persistent pain and difficulty moving signal a much deeper issue. 

Cancers with this symptom include:

• Osteosarcoma. Common in large and giant dog breeds, canine osteosarcoma is a malignant bone tumor that weakens the bones and increases the risk of fractures. 

• Lymphoma. Lymphomas can affect the joints of dogs, resulting in pain, inflammation, and reduced range of motion.  

• Soft Tissue Sarcomas. These tumors develop on the soft tissues of dogs, significantly affecting their comfort and ability to walk.

3. Lethargy or Collapse

If your dog appears weak for long periods of time or collapses suddenly, then it might be an indicator of cancer. Abnormal growths inside a dog’s body can impact its bodily function, resulting in a much weaker state. 

A general sign that can tell you if your dog has cancer is if they’re lethargic. Your dog might also appear easily fatigued. This is often seen after some physical activity, which is commonly referred to as exercise intolerance.

This includes cancers such as:

• Hemangiosarcoma. This type of cancer typically leads to internal bleeding in dogs, caused by the rupture of the blood vessels. 

• Heart Tumors. Abnormal growths on or near the heart can interrupt regular heart function, which impairs blood flow and oxygen delivery.

• Lung Tumors. Lung tumors hinder proper breathing in dogs, especially if they obstruct the airways. This leads to shortness of breath and reduced oxygen supply. 

4. Gastrointestinal Issues

Dogs can be picky eaters at times, but if your pup suddenly stops showing interest in food or starts eating more than usual, it can potentially point to cancer. For example, tumors and masses in the digestive tract can make eating uncomfortable. 

This ultimately results in weight loss. Additionally, weight loss can also be caused by the cancer cells themselves draining your dog’s resources.

Other symptoms, such as vomiting and diarrhea, which are possible signs of gastrointestinal cancer, can also cause weight loss. 

Cancers with these symptoms include:

• Gastrointestinal Cancer. Cancers within the GI tract can impair the absorption of nutrients and make it painful for dogs to eat. 

• Lymphoma. Lymphomas within the digestive system can lead to a reduced appetite, changes in metabolism, and malabsorption of nutrients. 

• Liver Tumors. Similarly, tumors on the liver can result in loss of appetite and metabolic changes. These result in weight loss.