All animals have different propensity to the development of cancers (malignancies) but dogs are unusual in that they can present with many of the cancers which also affect humans. To reassure those who do not know the disease process, cancers are not communicable and so a dog in the household which has a cancer which can affect humans cannot under any circumstances pass it on, any more than another person would. Dogs as a species have the dubious honour of being the only species other than man which can suffer from spontaneous prostate cancer development. While some cancers are difficult to ascribe a cause to, others have been proved to most professionals’ satisfaction to be caused by various environmental factors. This is easier to prove in an animal than a human and because of the medical ethics involved it is possible to treat animals with more aggressive drug regimes that are often very successful.
Mammary Cancer and its Symptoms and Prevention
One of the most common cancers found in dogs is of the mammary gland. One in four unsprayed bitches of the age of four and over will go on to develop a mammary tumour. The good news here is that only half of these will be malignant and they are quite treatable as the dog will probably give very early warning signs through behaviour that something is amiss. And of course a simple way of minimising the risk of this particular The tumour most often appears in the mammary glands nearest to the back legs and in the most aggressive form presents with similar symptoms to mastitis. It is usually diagnosed definitely when the usual antibiotic regime which would easily clear up mastitis has no effect. The tumour is likely to be painful and therefore it is unlikely to be missed. To a skilled professional a provisional diagnosis of malignant or benign tumour is possible, but it is always backed up by a biopsy. For reasons not yet identified, Springer Spaniels are particularly prone to breast cancer.
Prostate and Testicular Cancer
Testicular cancer can of course be prevented by the very simple course of neutering as there is no longer a site for the cancer to develop. Prostate cancer in the dog is rare but is often mentioned in literature because of it being a disease of dog and man only; no other creature suffers from it. Testicular cancer is easy to spot if the dog has a normal development. Sadly, the most commonly occurring cases of testicular cancer is in dogs when the testis has not dropped into the scrotum and so is often discovered relatively late. Despite this, it is quite easy to treat surgically, but unless the dog is of value to a breeder, prevention by castration is definitely better than cure. Bladder cancer is a much more common disease of the urino-genital tract and can be very insidious as it can be present for many months before symptoms show. These are usually retention of urine and bleeding and in a dog which is free to roam may be symptoms which are missed at the outset until the dog is quite ill. Terriers, and in particular Scottish terriers, are markedly prone to bladder cancer, sometimes called transitional cell cancer.
Cancers of the Bones, Bone Marrow and Lymphatic System
Dogs suffer from malignancy of the lymphatic system much more frequently than people, with an incidence of up to four times as many. Bone cancers are even more frequent, with an incidence of eight times the number found in humans. Lymphomas are usually not a serious condition in dogs, as long as treatment can start quite quickly and are considered non life threatening unless the animal is also ill in other ways. Bone cancer on the other hand is usually very serious, with a low survival of less than 10% after three years. This is partly because the dog will not always complain or show any signs of limping or favouring a limb. Because bone cancer is so prone to metastases (secondaries) it is usually sadly the case that it will have spread to some other part of the body before it is diagnosed. This is the main reason for its low survival rate – the initial tumour can often be dealt with relatively successfully. Retrievers, spaniels and boxers are particularly prone to lymphoma, greyhounds, rottweillers and other giant breeds to bone cancer.
Skin cancer is quite common in dogs, but a large proportion of the tumours associated with the skin are benign and even those which are malignant are fairly easy to treat, although early detection is, as always, very important. Many skin cancers can begin in places which may not be noticed, such as around the anus or in the nail beds and in these situations watching out for unusual behaviour in the dog, with excessive licking or biting is very important for early detection. Some breeds with thin hair can be particularly affected by skin cancers associated with sun damage and dark skinned breeds are also many times more likely to develop melanoma, which is aggressive and very serious. Dogs tend to develop skin malignancies very often in the mouth and in these cases fast treatment is essential or the surgery may need to be so radical that there is no real alternative but euthanasia for the animal’s comfort.
What to Watch for
The careful owner will always be on the lookout for changes in behaviour which may signal the onset of a serious medical condition but many types of cancer even total vigilance will not always be the answer. So often the symptoms are the same as some other much more common disease and time is lost in providing the wrong treatment. However, a dog which is generally healthy in other ways is more likely to survive cancer and if every effort is made to keep the animal in peak condition, even this most dreaded diagnosis can have a successful outcome.