The Top Signs of Cancer in Dogs

lethargic beagle; cancer signs in dogs

If you’re like many dog owners, then it’s likely your furry friend is part of the family. You do everything in your power to keep them happy and healthy. However, many people don’t want to think about the possibility of their dog getting cancer; they are then not aware of the cancer signs they can look out for indicating their dog may be sick. While cancer is not a fun subject to talk about, the risk that your dog will get cancer will drastically increase as they age. In fact, it is believed as many as 50% of dogs over the age of 10 will develop cancer.

Successful cancer treatment is often contingent on discovering the disease as early as possible; this makes it critical that pet parents are aware of signs indicating their dog may have cancer so they can get them the proper treatment. Dogs cannot express when it is in pain or discomfort; it becomes their human’s responsibility to look out for any changes which could signal a problem. Here are a few signs you can look out for in your dog which can indicate they may have cancer.

Weight Loss

One of the clearest signs of dog cancer you can be on the lookout for is unexplained weight loss. This is one of the most common cancer symptoms in canines. While many pet parents will know something is wrong, and will schedule an appointment with their vet; if their dog suddenly stops eating, you should also look out for sudden, unexplained weight loss. If your dog is eating and exercising the same amount as they normally do but they seem to be losing weight rapidly, this is generally a clear sign of cancer. In particular, gastrointestinal cancers often cause weight loss without showing any other visible symptoms. This makes it critical you get your pet seen by a vet as soon as possible if they’re losing weight.

Unusual Swelling or Growths

When you see a new or unusual lump or growth on your dog, or an existing growth seems to have suddenly changed size or shape, you will likely begin to worry that this growth is a sign of cancer. However, it’s important to note that as dogs age they may develop non-cancerous lumps and fatty deposits; these are benign. Regardless, it is smart to still be aware of any changes to your dog’s skin; and to have any new or changing lumps inspected by your veterinarian. Some lumps can be a sign of certain cancers such as skin cancer and mammary cancer. For this reason, it’s recommended you inspect your dog periodically for signs of lumps or tumors. You want to discover them, and have them looked at, as soon as possible after they appear.

Wounds Won’t Heal

A lesser-known sign of canine cancer is if your dog has a wound that won’t heal. If your dog cuts or injures themselves, then the wound should slowly show signs of healing over time such as scabbing, new skin growth, and hair regrowth. However, if your pet has cancer then their wounds may have a hard time healing, or the wound may start to heal and then reoccur. It is then important that you never ignore a wound that won’t heal; you should have your dog looked at if they have such a wound in case it’s caused by cancer.

Changes in Bathroom Habits

Considering you have to dispose of it regularly, it’s likely you are fairly familiar with your dog’s bathroom habits; including how frequently they go and what it looks like. You should then be concerned if you notice a drastic change in their bathroom habits. While occasional diarrhea and constipation are not necessarily causes for concern, if these problems persist or get worse then you should consider taking your dog to the vet as this could indicate a serious problem. In particular, you should look for a frequent/urgent need to go to the bathroom, difficulty going to the bathroom, and you should look for bloody or black and tarry stools, as these signs can indicate cancer.


While your dog may slow down as they age and not be as active as they were when they were a puppy, sudden lethargy (or lack of energy) should be a cause for concern. Lethargy is different than the occasional exhaustion that can come with aging or a busy day at the dog park. If your dog seems to suddenly not have any energy, is no longer excited by their favorite activity (such as playing fetch or going on a walk), or they no longer greet you when you come home from work, these can be signs of lethargy. Lethargy does not automatically mean that your dog has cancer. But there’s likely an underlying condition causing this problem which you’ll want to have checked out.

They Show Signs of Pain or Discomfort

An important sign of canine cancer to look out for is signs of pain or discomfort. While it is common for overactive dogs to occasionally injure themselves, which can cause mild pain for a few days, severe pain and/or pain that persists is generally a sign of something more serious. In particular, if your dog whines or cries when you pat their tummy, when you go to pick them up, or when they try to stand, then you will need to get them to the vet as soon as possible.

Frequent Coughing

Another lesser-known sign of canine cancer is if your dog suddenly develops a serious, chronic cough. While it is normal for your dog to cough occasionally, particularly in small breed dogs who tend to develop windpipe problem, if your dog begins coughing persistently, this may be a sign of lung cancer. A chronic cough can also be a sign of heart disease in some dogs. Either way, if your dog develops a serious cough that lasts more than a couple of days, you should not ignore it as this can be a sign of a serious illness.

Knowing when your dog is sick is critical in ensuring that they get the proper treatment, particularly with cancer.  Getting treatment as soon as possible is often crucial. Contact us to learn more about the signs you should be on the lookout for that can indicate canine cancer.

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