common cancers in senior pets

Cancers Associated With Old Age In Pets

Unfortunately, a common consequence of our pets becoming older is the occurrence of various cancers.

One of the most common cancers seen in primarily old dogs and rarely in cats, is mammary cancer.

Surgical removal is recommended for most mammary tumours.

The prognosis is good following surgical resection for MOST mammary tumours in female dogs, but the prognosis is worse for certain types of tumours in dogs and ALL mammary tumours in cats.

Mammary tumours are more common in female dogs that are either not spayed or were spayed after 2 years of age.
The risk of a dog developing a mammary tumour is about 0.5% if spayed before their first heat (approximately 6 months of age), about 8% after their first heat and about 26% after their second heat.
Cats spayed before 6 months of age have a 7-times reduced risk of developing mammary cancer and spaying at any age reduces the risk of mammary tumours by 40% to 60% in cats.

More than a quarter of un-spayed female dogs will develop a mammary tumour during their lifetime.

A second cancer to mention is lymphoma.

Lymphoma is common in both geriatric dogs and geriatric cats.

Lymphoma is a common neoplasm affecting both dogs and cats and results from the malignant transformation of lymphocytes. It often arises from primary and secondary lymphoid tissues, including the thymus, spleen, lymph nodes and gut-associated lymphoid tissues. However, because lymphocytes are capable of trafficking throughout the body, the development of lymphoma is not anatomically restricted. Common site for the spread of lymphoma include the skin, eye, central nervous system, testis and bone marrow.

Although lymphoma is considered a common neoplasm, a definitive cause for its development in dogs remains to be determined.

In cats, feline leukemia virus (FeLV) has been identified as a biologic carcinogen resulting in malignant lymphocyte transformation.
Often, lymphoma can affect the intestinal wall of your cat, causing symptoms of vomiting, diarrhoea and weight loss.

The oral cavity is a common site for neoplasia in cats, accounting for about 10% of all feline tumours.

The most common malignant oral tumour in cats is squamous cell carcinoma. The prognosis for this fast-growing, invasive tumour is grave once advanced, so it is vital to identify and treat it early.

Osteosarcoma accounts for only approximately 5% of all canine tumours, but is by far the most common bone tumour of the dog.  It is a malignant tumour of the bone and can develop in any bone, but most often occurs in bones bordering the shoulder, wrist and knee.

This cancer develops deep within the bone and becomes progressively more painful as it grows outward and the bone is destroyed from the inside out. Lameness may occur suddenly or start intermittently and progress over several weeks. Obvious swelling becomes evident as the tumour grows and normal bone is replaced by tumorous bone.

Osteosarcoma usually occurs in middle aged or elderly large and giant breed dogs but can occur in a dog of any age with larger breeds tending to develop tumours at younger ages.

Highly aggressive and metastatic in nature, over 90% of all clinically significant osteosarcomas have already metastasized by the time of diagnosis.  Most metastasis occurs in the lungs and other bones, but lymph node metastasis has been reported.

Canine haemangiosarcoma is also known as malignant haemangioendothelioma or angiosarcoma.

There are three types of haemangiosarcoma. Dermal when found on the skin, sub-cutaneous when found under the skin and visceral, when found in the organs like the spleen or heart. The spleen is where haemangiosarcoma is most commonly diagnosed and the prognosis in this area without treatment is poor.

These tumours are mostly found in middle aged to older dogs.

Dermal haemangiosarcoma appears as a red or black growth on hairless portions of your dog’s coat. Dogs like Dalmatons and bull terriers are at higher risk of the disease. Subcutaneous and visceral tumours appear on internal organs and there is often very little warning before they cause severe clinical signs. The average time for survival once a visceral tumour has been discovered is six to eight weeks.
Symptoms of haemangiosarcoma can depend on the location of the tumour. Your dog may show signs including lethargy, weakness, lack of appetite, coughing, weight loss and swelling of the abdomen.

In cats, the spleen and liver are the most common places for a hemangiosarcoma tumour to develop and grow.

Many times, cats with visceral hemangiosarcoma look and act normal and then suffer an episode of collapse or sudden death. That’s because the tumour, which affects blood vessels, has ruptured and the animal is bleeding internally. If the problem is diagnosed quickly enough, emergency surgery usually needs to be performed to remove the tumour.

Most of the time, cancerous cells have spread throughout the body through the circulatory system by the time the condition is diagnosed, even if surgery is done to remove the primary, actively bleeding tumour, pets usually become sick from the development of tumours in other areas, like the heart and lungs, shortly after initial diagnosis.

Symptoms to look out for include:
  • Weight loss
  • Enlarged abdomen
  • Coughing
  • Lethargy
  • Decreased appetite
  • Panting
  • Pale gums
  • Weakness

This condition is far more common in dogs than cats.


For more information on these, and other, common cancers found in pets, please visit these websites –

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