In this article I shall describe five common cancers found in dogs. I’ve included some of the symptoms of these cancers and you will see that many of them are also included in the 10 common signs of cancer in small animals that I listed in the last article.
The prognosis for the cancers I mention is not particularly good; the figures are broad generalizations, but they do highlight how important it is to to detect and treat cancer as early as possible to give your dog every chance of a successful recovery or good remission prospects.
Before we start, here are two more definitions; cancer can be divided into two broad categories:
- Carcinomas – malignant growths made up of epithelial cells (these are the cells that cover the lining of any body surface, such as skin, the bladder and blood vessels) that pass into the surrounding tissues and give rise to metastases (the spread of cancer cells);
- Sarcomas – malignant tumors that originate from connective tissue (such as bone, cartilage, muscle, blood vessels and lymph tissue). There is usually a prefix that describes the tissue of origin, for example, osteosarcoma is cancer of the bone.
Here is a list of 5 of the most common forms of cancer in dogs, and their symptoms:
1. Lymphosarcoma (Lymphoma)
This cancer is associated with your dog’s lymphoid system, which is an important part of his immune system.
Lymphoid tissue is found in many parts of the body including the lymph nodes, liver, spleen and skin. The most common form of lymphoma in dogs is the multricentric form that occurs in the lymph nodes.
Symptoms of lymph node cancer are swellings of the lymph nodes, and there are 5 major lymph nodes that you can feel on your dog – click here for a diagram showing the location of the external lymph nodes.
Other forms of lymphoma will show symptoms such as vomiting, weight loss and lack of appetite (gastrointestinal form), shortness of breath (chest form) and single or multiple lumps in the skin or in the mouth (skin (cutanaous) form)).
Middle aged to older dogs (aged approximately seven to ten years) are more prone to lymphoma, and no breed is particularly susceptible. The cancer can be very aggressive, and if left untreated the prognosis is a matter of weeks. With treatment your dog’s life can be extended by several months to a year.
This cancer originates from the cells that form your dog’s blood vessels and can occur in any part of your dog’s body, but is mainly found in the spleen, liver, heart and skin.
The first sign of the cancer being present is usually a ruptured tumor, and because the tumor is formed from blood vessel cells, it is often full of blood.
If the tumor is in the liver or spleen, the ruptured tumor will cause anemia and weakness in your dog through the loss of blood.
If the tumor is present in your dog’s skin, then a lump may be felt under the skin, and if it’s in the bones then a swelling of the bone may be felt.
Hemangiosarcomas usually occurs in older dogs, and some breeds seem to be predisposed to it – Golden Retrievers, German Shepherds, Portuguese Water Dogs and Skye Terriers.
The tumors aren’t usually detected until their late stages, in internal organs this is usually when the tumor has ruptured, and the prognosis is poor; less than 50% of dogs will survive more than 6 months. Survival rates are better when the cancer occurs in the skin because it can usually be detected and treated earlier.
This is cancer that originates in your dog’s bones, more usually in the limbs but can occur in any part of the skeleton.
Large dog breeds are more prone to osteosarcoma – Great Danes, Saint Bernards, Great Pyrenees, Newfoundlands, Bernese Mountain Dogs, and Irish Wolfhounds in particular. Heavily built dogs such as Rottweilers, Labradors, Golden Retrievers, German Shepherds, Dobermans, Weimaraners, and Boxers are also at an increased risk.
The symptoms include lameness, pain in the bones, swelling, and reluctance to exercise. 90% of osteosarcomas spread to the lungs and so your dog may show symptoms such as coughing and difficulty in breathing too. Unfortunately the cancer is rarely detected before it has spread from the bones to other parts of the body.
The prognosis is poor; less than 50% of dogs will survive more than a year.
4. Mammary Carcinoma
Mammary tumors are the most common tumor in female dogs that haven’t been spayed – the risk of your dog developing this cancer is almost eliminated if she is spayed before her first season.
Provided the tumor is detected early enough, this cancer can usually be successfully treated. The symptoms are a solid mass or numerous swellings in the mammary glands; they tend to start off small and grow quickly grow in size.
As the cancer can spread to other parts of your dog’s body, any unusual swelling in the mammary glands should be investigated by your vet as soon as possible so that any malignant tumor can be treated.
5. Mastocytomas (Mast Cell Tumors)
Mast cells form part of the body’s tissue and play a role in the body’s immune system.
Mastocytomas are most commonly seen in the skin, and can spread to the lymph nodes, spleen, liver and bone marrow. These tumors usually occur in older dogs.
Symptoms include raised masses on or under the skin – single or multiple lumps, which may be smooth, bumpy or ulcerated. Your dog may also show a lack of appetite, vomiting and abdominal pain.
The prognosis depends upon how far advanced the cancer is; broadly if the tumor is on your dog’s limbs then he has a better prognosis than if the tumor is in the nail bed, genital areas and mouth. Mast cell tumors in the internal organs have a poor prognosis.
Not a great deal is known about this form of cancer – because it does not occur in humans, less research has been undertaken.
As I mentioned the first article – Dog Cancer Facts – there are many, many forms of cancer, and each is a disease in its own right which has it’s own specific treatment and prognosis.
In the next article I’ll give you 10 tips for facing cancer should your dog be diagnosed with a malignant tumor.