Cancer is the leading cause of death in dogs with 1 in 4 getting cancer in their lifetime and 1 in 2 over the age of 10 succumbing to the disease*. As cancer does not discriminate, it is important to know how to check your dog for warning signs.
In this guide, I will walk you through some of the early warning signs of cancer in dogs, how to identify them, and when to seek veterinary advice. As a Specialist in Veterinary Oncology at SASH, I hope this helps you better understand when a change may need further investigation.
*Gardner et al (2015), Annu Rev Anim Biosci. 9;4:199–222, Adams et al (2010), J Small Anim Pract;51(10):512-24, MacEwan (1990), Cancer Metastasis Rev.;9(2):125-36
Key Early Signs of Cancer in Dogs
- Lumps and bumps on and under the skin
- Abnormal smell from the mouth or ears
- Non-healing wounds or sores
- Loss of appetite or weight loss
- Persistent coughing or difficulty breathing
- Changes in drinking or urination
- Difficulty chewing or swallowing
- Changes in bathroom habits
- Signs of pain, including lameness
- Reduced energy levels
Signs of cancer in dogs infographic
Video: 10 signs of Cancer in Dogs
What are the Warning Signs of Cancer in Dogs and How to Identify Them
1. Lumps and bumps on or underneath your dog’s skin
A lump or bump on or under your dog’s skin can be a sign that something is not quite right. While some lumps are harmless, others may need investigation by your vet.
Gently run your hands over your dog’s body to check for any unusual lumps or bumps. While it is not possible to tell whether a lump is cancerous just by touch, noticing new lumps or changes early can help your vet understand when further testing may be needed.
Lumps can appear anywhere on the body, including between the toes, so it’s great if you can train your dog to be comfortable with you looking at and touching their feet. A good habit to get into is checking your dog all over monthly.
2. Abnormal smell from the mouth, ears, or other parts of your dog’s body
An unusual smell coming from your dog’s mouth, ears, or another part of the body can be a sign that something is wrong. In some cases, this may be related to dental disease, infection, or an underlying tumour.
While abnormal odours are not always linked to cancer, they should not be ignored, particularly if the smell is new, persistent, or accompanied by other symptoms.
3. Non-healing wounds or sores
Persistent, non-healing wounds or sores can be a sign that your dog’s immune system isn’t functioning properly, or is busy combating another infection or underlying disease.
Some cancers can also appear as persistent sores or skin lesions, especially if they are changing, bleeding, or not improving over time.
4. Loss of appetite or weight loss
A reduced appetite or unexplained weight loss can be an early sign that your dog is unwell. Sometimes this is linked to dental, digestive, or other medical issues, but it can also point to more serious underlying disease, including cancer.
This is especially important to investigate if the change is out of character for your dog, happens quickly, or appears alongside other warning signs.
5. Coughing or difficulty breathing
A persistent cough or any noticeable change in your dog’s breathing should be taken seriously. While there are many possible causes, these symptoms can sometimes be associated with cancer affecting the lungs, airways, or chest.
Dogs don’t really get colds and coughs like humans, so if coughing continues for more than a couple of days, or your dog seems short of breath, it is worth having them checked promptly.
6. Increased drinking or frequency of urinating
Drinking more water than usual, needing to urinate more often, or asking to go outside repeatedly can all be signs that something is not right with your dog.
These changes can be linked to a range of medical conditions, including some cancers and metabolic illnesses, so they should not be ignored.
7. Difficulty chewing or swallowing
If your dog seems to have trouble picking up food, chewing, or swallowing food, water, or saliva, this may indicate a problem affecting the mouth, throat, or neck.
Difficulty swallowing can have several causes, including inflammation, infection, or cancer, and should be assessed by a vet as soon as possible.
8. Changes in bathroom habits
Changes in your dog’s usual bathroom habits can be a sign of illness. This may include straining to urinate, difficulty passing faeces, changes In the shape of the faeces, or going more or less often than normal.
Sometimes these changes can be caused by infection or inflammation, but they can also be associated with growths or cancers affecting internal organs.
9. Signs of pain or discomfort, including lameness
Some cancers, particularly bone cancer, can cause pain that shows up as limping, stiffness, lameness, or reluctance to move normally.
If your dog seems uncomfortable doing things they would usually do with ease, it is worth arranging a check-up. Arthritis is also common in older dogs, so it is important to work out what is causing the change in order to treat it. It is important to treat pain to ensure your dog’s quality of life is the best it can be.
10. Reduced energy levels
If your dog seems unusually tired, less interested in walks, or reluctant to take part in their usual activities, this may be a sign that they are unwell.
Reduced energy levels can be associated with many conditions in older pets, including heart disease, arthritis and cancer, and are worth discussing with your vet.
What Do I Do if My Dog Shows Signs of Cancer?
If your dog is showing one or more cancer warning signs, the next step is to have them assessed by a vet. Many of these symptoms can have causes other than cancer, so they should be checked – especially if they are persistent, worsening, or happening alongside other changes.
Your vet can perform a thorough examination and recommend any tests needed to better understand what may be causing the change. Depending on your dog’s symptoms and the findings of that assessment, they may suggest monitoring, further diagnostics, or referral to a specialist team such as Internal Medicine, Surgery, or Dermatology.
If cancer is diagnosed, treatment will depend on the type of cancer, how advanced it is, and your dog’s individual needs. Options may include surgery, chemotherapy, radiation therapy, immunotherapy or a combination of these treatments.
At SASH, pets with confirmed or suspected cancer can be referred to the SASH Cancer Centre, where Oncology Specialists work with multidisciplinary teams to provide advanced diagnosis and treatment. Every treatment plan is tailored to the individual pet, while also taking into account the goals of treatment and the wishes of the family.
What Outcomes Can I Expect From Cancer Treatment?
Outcomes from cancer treatment can vary widely from one dog to another. They depend on several factors, including the type of cancer, how advanced it is, where it is located, and your dog’s overall health.
In some cases, treatment may aim to cure the cancer. In others, the focus may be on slowing its progression, managing symptoms, and maintaining the best possible quality of life for your dog for as long as possible.
The good news is that advances in veterinary oncology mean there are now more treatment options available for dogs with cancer than ever before. Your vet or oncology team can talk you through the likely outcome for your dog, the goals of treatment, and the options that may be most appropriate for their individual case.
If you have concerns about signs of cancer in your dog, please click the contact button below to book an appointment.
Frequently Asked Questions About Cancer in Dogs
What do cancerous tumours look like on dogs?
Cancerous tumours in dogs can look very different depending on the type of cancer and where it is located. Some appear as lumps under the skin, while others may look like swollen areas, sores that do not heal, ulcerated or crusted skin, or changes around the toes or nails. As cancerous tumours can look similar to non-cancerous lumps, the only way to know for sure is to have them checked by a test with a vet.
Are all dog tumours cancerous?
No, not all dog tumours are cancerous. Some tumours are benign, which means they do not spread to other parts of the body. Others are malignant, which means they are cancerous and may invade nearby tissue and spread. As you cannot tell the difference just by looking or feeling a lump, any new or changing tumour should be assessed by a vet.
Can dogs get skin cancer?
Yes, dogs can get skin cancer. In fact, tumours affecting the skin or the tissue just under the skin are among the most seen tumours in dogs. Skin cancer can appear in different ways, including lumps, sores, irritated skin, or non-healing lesions. Any unusual skin change is worth having checked.
What causes cancer in dogs?
Cancer in dogs does not usually have one single cause. It is thought to develop because of a mix of factors, including age, genetics, environmental exposures, and, in some cases, nutrition or hormones. In many dogs, the exact cause of an individual cancer cannot be identified.
How can you tell if your dog has cancer?
You cannot tell for certain if your dog has cancer based on symptoms alone. Warning signs can include lumps, weight loss, reduced appetite, coughing, changes in bathroom habits, lethargy, or sores that do not heal, but these signs can also happen with other illnesses. A diagnosis usually requires a veterinary examination and, depending on the case, tests such as bloodwork, imaging, or a biopsy.
Are some dog breeds more prone to cancer than others?
Yes, there is evidence to suggest that some dog breeds are more prone to cancer than others. For example, large dog breeds are more likely to get bone cancer, and Scottish terriers are at an increased risk of developing bladder cancer. Research and clinical data suggest that breeds such as Golden Retrievers, Boxers, Bernese Mountain Dogs, and Rottweilers have higher cancer rates overall, which suggests breed genetics can play a role.
Can a dog have cancer and show no signs?
Yes, a dog can have cancer and show no obvious signs. Some cancers are only found after routine physical examination, tests, imaging, or when a dog is examined for something else. That is a reason persistent changes, even subtle ones, should be examined by a veterinarian, and a good habit to get into is checking your pet all over
Can cancer be treated in dogs?
Yes, cancer can be treated in dogs. The most appropriate treatment depends on the type of cancer, how advanced it is, your dog’s overall health and your family’s circumstances. Common treatment options include surgery, chemotherapy, radiation therapy, immunotherapy or a combination of these. In some cases, treatment aims to cure the cancer, while in others the focus is on slowing progression and maintaining quality of life.
What are the side effects of chemotherapy like?
Unlike in people, side effects of chemotherapy in dogs is uncommon. Roughly 10-20% of our patients experience mild side effects (not wanting to eat, nausea, diarrhoea) that can be treated with medications at home. Less than 5% of patients end up in hospital from chemotherapy side effects and <1% die from treatment. While uncommon, if these side effects occur in your dog they can be serious and need veterinary attention.
How much does cancer treatment cost?
The cost varies widely depending on the cancer and what is used to treat it. It can vary from a few hundred dollars a month to thousands, and SASH always strives to work within your budget. During a consultation, your oncologist will give you detailed estimates to help you make an informed decision.
BVSc(Hons I) DACVIM(Oncology) MANZCVS
Dr Sandra Nguyen, DVM MANZCVS DipECVIM-CA (Oncology), is a Specialist in Veterinary Oncology at the SASH Cancer Centre in NSW. She completed her oncology residency at Cornell University, USA. She later served as a member of faculty at The Ohio State University before moving back to Australia to join the SASH team.
