Adenocarcinoma in Dogs - Causes, Sign and Treatment

Adenocarcinoma is the malignant version of adenoma. It is a type of malignant epithelial tumor, meaning it is a carcinoma that has its origin in the glandular tissue that covers certain internal and external organs.

Being malignant tumors, adenocarcinomas:

• Are locally invasive: this means they tend to invade surrounding tissues.
• Produce metastases: they spread cancer cells to other tissues. The rate of growth of these tumors is variable, but metastases are unfortunately very common. Initially, these tumors metastasize to the regional lymph nodes. They then spread from the lymph nodes, causing distant metastases in other organs.

Some of the types of adenocarcinomas in dogs that have been described include:

• Breast adenocarcinoma
• Nasal adenocarcinoma
• Laryngeal adenocarcinoma
• Pulmonary adenocarcinoma (lungs)
• Ceruminous gland adenocarcinoma (external ear)
• Parathyroid adenocarcinoma
• Sweat gland adenocarcinoma
• Gastric adenocarcinoma
• Intestinal adenocarcinoma
• Renal adenocarcinoma
• Anal sac adenocarcinoma
• Adenocarcinoma of the perianal glands

Adenocarcinomas most commonly present in dogs between 7 and 12 years of age. Depending on the specific type of adenocarcinoma, there seems to be a certain predisposition according to breed and sex. For example, anal sac adenocarcinoma is more common in German Shepherds, Cocker Spaniels and Springer Spaniels, especially females and neutered males.

As a general rule, tumors usually produce non-specific symptoms. This means the signs of adenocarcinomas in dogs are often those that also appear in many other diseases. In addition, as it can occur in a multitude of organs, the symptoms can be very diverse. The tumor can cause a malfunction of this organ which can result in systemic symptoms.

Below, we mention some of the common clinical signs that can be associated with this type of tumor:

• General signs: anorexia, weight loss, weakness, tiredness, pain, fever, anemia, polyuria (increased urine volume) and polydipsia (increased water consumption).
• Digestive signs: such as vomiting and diarrhea (often bloody), tenesmus (difficulty defecating) and hematochezia (blood in the dog's stool).
• Respiratory signs: such as tachypnea (increased respiratory rate), dyspnea (shortness of breath), exercise intolerance, sneezing and nose bleeds (epistaxis).

Like all neoplasms, adenocarcinomas are caused by a genetic alteration that gives rise to massive and disorganized cell proliferation. The specific cause that triggers this abnormal cell proliferation is unknown. It has been proposed that exposure to certain contaminants (such as mercury) may favor the development of this type of tumor. Further researh is required to know more about the causes of adenocarcinomas in dogs.

A differential diagnosis carried out by a qualified veterinarian is required to confirm this type of canine cancer. The following actions help guide the diagnosis of adenocarcinoma in dogs:

• Clinical signs: these will be accompanied by a physical examination of the animal.
• Blood tests: in some cases anemia, increased white blood cells (leukocytosis), decreased total protein (hypoproteinemia), hypercalcemia and increased alkaline phosphatase may be observed. However, in some cases, blood tests remain normal. Read our related article to learn how to understand a dog's blood test.
• Imaging tests: such as X-rays, ultrasound, MRI and/or endoscopy. These tests allow the detection of abnormalities in the primary affected organs and in the organs with metastases. The type of test required can depend on the likely location of the tumor.

These diagnostic tests only allow an approximation of the diagnosis. To reach a definitive diagnosis, it is necessary to perform a biopsy of the affected tissue to carry out a histopathological study in laboratory conditions. Observing the biopsied tissue under a microscope will not only reveal the type of tumor and its degree of development, but will also provide important information for the prognosis of the animal.

It is also important to perform a cytology of the regional lymph nodes. This is performed to rule out the existence of metastases in other tissues. Learn more with our article on the causes of a dog's swollen lymph nodes.

The treatment of canine adenocarcinomas is surgical. As it is a malignant tumor, it is necessary to perform a radical excision of the tumor, leaving wide safety margins to avoid recurrences. This requires removing some healthy tissue, where possible. It is also necessary to remove the regional lymph nodes and analyze them to ensure the absence of regional metastases.

In some cases, surgery can be complemented with postoperative chemotherapy treatment for dogs. Drugs which may be used include carboplatin, cisplatin, piroxicam or melphalan. Adenocarcinoma in dogs is curable, but this does not mean that there can be no metastasis.

The prognosis of these patients is reserved. The life expectancy of a dog with adenocarcinoma largely depends on the extent of the cell proliferation and whether metastasis has occurred at the time of surgery. Their general state of health will also bear importance. For all these reasons, it is very important to go to the veterinary center at the sign of any symptom which may indicate presence of cancer. The sooner it is diagnosed, the better the prognosis.

This article is purely informative. AnimalWised does not have the authority to prescribe any veterinary treatment or create a diagnosis. We invite you to take your pet to the veterinarian if they are suffering from any condition or pain.

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