Types of Dog Cancer

It’s tempting to think that dreaded disease, cancer, is purely a human ailment but almost all animals – including dogs – can suffer its different varieties and forms, so to start, let’s walk though some definitions and outline some of the types of dog cancer.

Firstly, if you spot a lump or growth somewhere on your pet, it doesn’t necessarily mean he has cancer.

Lumps or tumours are simply the uncontrolled growth of cells which might do nothing worse than push organs out of the way, interrupting their normal function. Of course, that might lead to problems of their own – perhaps even serious ones – but tumours that stay put are generally termed “benign” and not cancerous and, in most cases, can be surgically removed with no harm done.

Cancer is a term reserved for those tumours which might spread, and are described as “malignant”, and sadly, statistics show that almost half of all pets aged 10 or more will fall victim to types of dog cancer.

Take for example mammary cancer in dogs. It can occur in any of her 10 mammary glands but in about half of all cases such tumours are completely benign. Spayed bitches are also much less likely to get breast cancer, and so post-op treatment usually includes spaying, if applicable, to reduce the chance of a reoccurrence. Dog mammary cancer life expectancy can vary widely from just a few months in the most advanced cases, to dogs living out the rest of their lives normally after surgery to excise small cancers which don’t then get the opportunity to spread. Like humans, male dogs can also suffer from breast tumours, but the incidence is very rare, and most lumps turn out to be benign anyway.

Because of their proximity, one common complication of malignant breast cancer in dogs can be spread to the lungs, so before any surgery to remove tissue, your vet will probably take chest x-rays just to make sure. Standalone symptoms of lung cancer in dogs include obvious signs of pain, difficult or rapid breathing, coughing up blood, lethargy, poor appetite and gradual weight loss. By the time he becomes lame you should be aware that his cancer has spread to his bones. Bone cancer in dogs is one of the more painful types of the disease, leading to general aches and pains and ultimately to debilitating fractures.

The lungs are also at risk of secondary tumours in cases of stomach cancer in dogs or cancer of the bowel. Bowel cancer in dogs and other cancers of the gut can be especially distressing for you and your dog because it affects his ability to eat, and may lead to incontinence or diarrhoea. Classic symptoms include chronic vomiting, loss of appetite and weight loss but you may also be disturbed to find vomit in blood and stools.

Sadly, by the time most dogs are diagnosed with this type of cancer, around 3 in 4 will already have secondary conditions, and in such cases the average survival time after surgery is a little more than 2 months. Dogs can also suffer from skin cancer which may be linked to sun exposure although in this instance most skin lumps are benign and so can easily be removed unless the tumour is large or sited in an area where repairing the skin might be difficult. Lumps which spontaneously reoccur in the same place are more serious and there is a chance that they may also spread. If a biopsy reveals a more aggressive tumour then cutting out larger areas of tissue can reduce the chance of spread or reoccurrence. One of the most common dog skin cancers are Mast Cell tumours. Mast Cells are usually found in the connective tissue of the body, especially in organs close to the external surfaces, for example the lungs, nose, mouth and the skin itself. They affect a type of blood cell normally involved in the body's response to allergens and inflammation. Mastocytoma – or MCT – can also affect other areas of the body, including the spleen, liver, gastrointestinal tract, and bone marrow. The condition usually appears in dogs aged eight or older, although it has been reported in puppies too.

Veterinary surgeons report that they are seeing more and more malignant lymphoma in dogs, a tumour of the lymph nodes, bean-shaped masses of tissue, that help to protect against infection by collecting and killing bacteria and neutralizing toxins. The lymph nodes also the source of lymphocytes, also known as white blood cells. If lymphocytes become cancerous and so start multiplying uncontrollably, the nodes may swell, producing lumps in the throat which may make swallowing harder, and even spread to other parts of the body and internal organs via the lymphatic system or blood supply. Cancer of the liver, bladder and pancreas sometimes follows.

Surgery is not usually enough on its own to halt the spread of lymphoma cancer in dogs, and without other options like chemotherapy, survival time is again only about two months. Even aggressive treatment with drugs or radiation may only extend life for around 12 months. Dogs suffering canine lymphoma are not in pain but may become ill because of the spread to other organs.

And again, as with humans, symptoms of brain tumours in dogs may result in mood swings or changed behaviour such as an increase or decrease in thirst or hunger, constant pacing or circling, reduced awareness and vision on one side of the body, pain and seizures. This is one case where a benign tumour which is impossible to remove may cause problems by applying pressure to parts of the brain or nervous system. Symptoms typically start off mild and get worse, but they can also start quite suddenly. In some cases, they vary in severity from one day to another, sometimes getting better, sometimes worse.

All of this may sound pretty frightening for any owner but it’s wise to remember that much of the reason that more dogs are presenting with cancer symptoms is that owners today are much better able to care for their animals who are, in turn, living longer, to the age where cancer becomes more common.

In the past, many dogs died from common illnesses or were killed in road traffic incidents. The increase in the routine use of vaccines and other medicines, and the increasing tendency not to allow dogs to roam free on the streets, means they’re just around longer.

In fact, however, but most cancers in dogs can be successfully treated with surgery. Even in situations where the disease may have advanced to a lymph node, there are options to prolong your dog’s life and even cure him.

What are the warning signals that your pet may be in pain, and what should you do?

The key is early diagnosis. Signs of cancer in dogs might include an unexpected lump or a bump, a wound that won’t heal, swellings, enlarged lymph nodes, lameness or swollen joints or abnormal bleeding. Other symptoms common to many different cancers from Bowel to Thyroid include excessive thirst, weight loss, difficulty in swallowing or breathing, and increased frequency of passing urine.

Sometimes, however, there is little or no warning, so if your dog isn’t feeling well or you simply know in your heart that something’s not quite right, it’s always best to consult a vet.

There are some things which will reduce your dog’s chances of developing cancer, the best of them is spaying. Spaying her before her first heat reduces her chances of developing mammary cancer by almost 90%. Good oral care, including synthetic bones, chew toys, dry food and even teeth cleaning, can help decrease dog mouth cancers. Your dog’s bad breath may itself be a sign of cancer. If you’re considering buying a pedigree, check back through the bloodline for any specific conditions.

There does seem to be a genetic component to some forms of cancer and it’s now understood that some breeds are just more likely to develop cancers than others. For example, boxers, beagles, and golden retrievers have a strong incidence of thyroid cancer in dogs. Labradors also suffer higher than average occurrence of pancreatic cancer in dogs. Boxers, bulldogs, pugs, and Boston terriers are prone to MCT. Staffordshire Bull Terriers have a higher than average incidence of bowel cancer. Some of this is thought to be the result of in-breeding from a small number of animals, which can increase the chances of defective genes being passed on.

On the other hand, mixed-breed dogs like Cock-a-Poos, Labradoodles or even flat-out mongrels, come from a much deeper gene pool and so are possibly less likely to get such genetic-based cancers. Owners of pure breeds shouldn’t beat themselves up too much, however, because the role of environmental factors, or even spontaneous influences, is not well understood.

Today, treatment for dogs with cancer very much mirrors that available for humans, from surgery to chemotherapy and radiation treatment. The survival and cure rate can be as high as 3 in 5 depending on the type of cancer and the individual animal and dog cancer life expectancy varies on the location and progression of the tumour before diagnosis. There are lots of dogs who have a simple “lumpectomy” and for whom there is a very good long-term prognosis, but severely-afflicted animals, if left untreated, might live only a few months.

Practically speaking, since cancer happens in the final years of your pet’s normal life, there is the humanitarian consideration that lengthy, costly and uncomfortable treatments which might delay their passing for a short time may not be the best thing for you or your dog.

The decision is your alone, but dog euthanasia may ultimately be the best course of action.