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Tumour behaviour in Dogs

Prevalence of cancer, which means number of diagnosed cancer cases per year, is increasing through years for a variety of reasons, but mostly because of animals living to increasingly older ages and the availability of better health care treatments. Cancer diseases stay the major cause of pet animal death. One of the big difficulties with animal cancer is that the pet cannot tell when he feels something wrong is happening, thus the owners need to bring every change to the attention of their veterinarian. Recognition of tumour related symptoms can facilitate early tumour diagnosis and treatment.                                      


Definition of a tumour

A tumour is an abnormal growth of cells on or within the body and may be benign (slow growing, without spreading throughout the body) or malignant (aggressive, with a tendency to metastasise). Cancer can affect any area of the body or any body system. A cellular diagnosis based on a biopsy or a fine needle aspiration of the tumoral cells is required to determine the type of cancer. Each tumour type within a location has a different behaviour, treatment and prognosis.


Clinical signs directly due to cancer

The warning signs of cancer in dogs are very similar to that in people, because they share the same types of tumour. Some common type of cancer in dogs include skin tumour, mammary gland tumour, testicular tumour, bone tumour, lymphoma... In many instances malignant tumours arising in the organs of the body will cause symptoms directly related to the location of the tumour.

Such symptoms are alarming when they become chronic and may include:










Canine paraneoplastic syndrome

Paraneoplastic syndrome is a symptom or a group of symptoms that are non-specific and consequence of the presence of a tumour in the body. Those disorders are indirect and are usually caused by tumour cell secretions, that is to say small molecules released in the circulation. Thus they may be seen at sites distant from the location of the tumour.


The paraneoplastic syndrome parallels the underlying tumour, and, therefore, successful treatment of the cancer leads to disappearance of those symptoms. Sometimes the symptoms of this syndrome show before the diagnosis of the tumour, and the recognition of them might be helpful for an early tumour diagnosis. Such disorders include loss of appetite, lethargy, weight loss/ poor body condition, fever, increased water intake (more than 100 mL/kg/day) and urination.


Some endocrinologic manifestations may also be related to cancer. For example, hypercalcaemia, which clinical manifestations are vomiting and increased water intake, is commonly related to lymphoma or anal tumour. Hypoglycaemia might also be associated to cancer, mostly secondary to a pancreatic tumour. Its clinical expression include weakness, disorientation and seizures.


It is important to keep in mind that those symptoms are completely non-specific and may be due to another cause than cancer.  Early diagnosis and treatment are key to a favourable prognosis, whatever the cause of the symptoms.


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