Thyroid Cancer in Dogs

A Pet Owners Guide to Thyroid Cancer in Dogs: Causes, Symptoms, and Treatment

Katelyn Son
By Katelyn Son
Medically reviewed by Jamie Freyer
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What is Thyroid Cancer in Dogs? 

What is Thyroid Cancer in Dogs

Thyroid cancer in dogs is a tumor that develops when the normal thyroid cells start to grow and reproduce abnormally, transforming into cancerous cells.

The thyroid gland lies along the dog’s trachea (windpipe), halfway down the neck. It consists of two lobes and makes thyroid hormones. The thyroid hormones regulate many vital body functions.

What is a Thyroid Tumor?

A thyroid tumor is a mass of cancerous cells in the thyroid gland. Thyroid tumors in dogs can be benign or malignant. Benign thyroid tumors are called adenomas, while the malignant are adenocarcinomas.

Benign thyroid tumors in dogs grow large and are usually functional, meaning they produce thyroid hormones which leads to a condition known as hyperthyroidism.

Malignant tumors are smaller and non-functional but spread to other body parts (lymph nodes, lungs, larynx, blood vessels, and esophagus). They also damage the normal thyroid tissue, causing hypothyroidism.

In dogs, most thyroid tumors are malignant and result in metastatic disease. Based on VCA Hospitals, thyroid adenomas are rare and account for only 10% of all thyroid tumor cases.

How Common is Thyroid Cancer in Dogs?

Thyroid cancer in dogs is not a common type of cancer. According to PetCure Oncology, they account for between 1.2 and 3.8% of all canine cancer cases.

Thyroid cancer in dogs is prevalent among seniors (over the age of 9) and certain breeds, such as Golden Retrievers, Beagles, Boxers, and Siberian Huskies.

How Quickly does Thyroid Cancer Spread in Dogs?

Thyroid cancer in dogs spreads rather quickly. Thyroid adenocarcinomas are classified as highly invasive and linked with severe metastatic disease forms.

According to Blue Pearl Vet, thyroid cancer has already spread to other body parts by the time of diagnosis in up to 35 to 40% of the cases.

What Causes Thyroid Cancer in Dogs? 

What Causes Thyroid Cancer in Dogs

The exact cause of thyroid cancer is not known. Like most canine cancers, it is triggered by a combination of risk factors. However, the usual dietary and nutritional risk factors do not seem to play a role in developing thyroid cancer in dogs.

Here is a short review of the factors that contribute to thyroid cancer in dogs:

  • Genetics. The genetic component is visible since the condition is more common in certain dog breeds (Siberian Huskies, Golden Retrievers, Beagles, and Boxers).
  • Age. Like most tumors, thyroid cancer in dogs seems more common in older dogs. Usually, it affects dogs over the age of nine.

What are the Signs of Thyroid Cancer in Dogs? 

The telltale sign of thyroid cancer in dogs is a lump in the cervical (neck) area. The lump may be fixed or movable and may or may not be painful to touch.

Other clinical signs and symptoms of thyroid cancer in dogs include:

  • Difficulty breathing
  • Difficulty swallowing
  • Changes in the bark
  • Facial swelling
  • Weight loss
  • Loss of appetite
  • Increased thirst
  • Frequent urination.

Some of these signs are specific, but others are universal and associated with various conditions. Therefore, pet owners are advised to seek immediate veterinary attention if their dogs exhibit some of them.

Diagnosing Thyroid Cancer in Dogs 

The diagnosis of thyroid cancer in dogs starts with a physical examination in which the vet may feel a palpable mass in the dog’s cervical area. The mass may be moveable or not.

If the veterinarian suspects tumor cancer, they will perform either a biopsy or a fine-needle aspiration (sometimes both). The collected tissue or cellular samples are analyzed under a microscope, which is enough to set a definitive diagnosis.

Then, blood work is usually done to test the thyroid hormone levels and assess whether the tumor is functional. Increased thyroid hormone levels (hyperthyroidism) indicate benign tumors and decreased levels (hypothyroidism) of malignant tumors.

The vet will order additional tests such as urinalysis, thoracic x-rays, chest radiographs, abdominal ultrasound, etc. More advanced imaging tests like MRI and CT scans.

How do You Treat Thyroid Cancer in Dogs?

How do You Treat Thyroid Cancer in Dogs

Cancer in dogs treatment is complex and often requires combining several approaches. The most common treatment options for thyroid cancer in dogs are surgery, chemotherapy, and radiation therapy.

Surgical Removal. Surgery is the treatment of choice for moveable thyroid tumors that are not spread to other organs. Considering the number of blood vessels in the region, removing thyroid masses can be challenging. Post-surgery, dogs need monitoring of their calcium levels ( during the surgery, parts of the parathyroid glands are often removed, and these glands are responsible for regulating the dog’s calcium levels).

Chemotherapy. Chemotherapy is the ideal treatment option for dogs that show evidence of metastasis. Generally speaking, thyroid cancer in dogs is moderately responsive to chemo. Dogs handle chemotherapy better than humans (with fewer and lesser side effects). Chemo is usually combined with surgery.

Radiation Therapy. Radiation therapy can be traditional or based on the use of radioactive iodine. Radioactive iodine is effective in the treatment of canine thyroid carcinoma. The dog is given radioactive iodine (orally), which destroys the cancer cells in the thyroid tissue once it reaches the target site. Radiation is recommended for dogs that are not candidates for surgery and dogs that have undergone surgery but show signs of severe vascular invasion.

In addition to these mainstream treatment options, you can talk to your veterinary oncologist about holistic cancer treatments.

Cannabidiol (CBD) Products. Cannabidiol (CBD) for dogs is the latest trend in the pet care industry. CBD may support thyroid cancer in dogs treatment in various ways – from relieving pain to reducing inflammation. When choosing CBD for your dog, you should only opt for pet-safe vet-approved brands like Honest Paws.

What can I do to Prevent Thyroid Cancer in Dogs?

There is no single answer to the question of how to prevent cancer in dogs. As dog owners, the best you can do for your pets is provide a healthy lifestyle that supports overall well-being.

A healthy lifestyle is an umbrella term that includes a nutritious diet, regular physical exercise, using pet-safe products, and regular checkups with your vet.

If your dog is diagnosed with thyroid cancer, the goal is to provide the best cancer treatment possible. Sadly, the treatment for canine tumors can be costly.

This is where pet insurance policies come in handy. We suggest the OneVet insurance policy. The policy gives you 24/7 access to a licensed vet, a $3000 emergency fund, and coverage for all pre-existing conditions, all for just $19.99 a month.

How Long Can Dogs Live With Thyroid Cancer?

How Long Can Dogs Live With Thyroid Cancer

The median survival time of a dog with thyroid cancer is about 24 months. The exact survival time for dogs with thyroid cancer depends on the size of the tumor, stage of cancer, and the quality of treatment.

If the surgery is a success, the dog can live up to 36 months. However, some dogs die within a year of diagnosis, often due to late diagnosis and inadequate treatment.

Can My Dog Survive Thyroid Cancer?

Yes, your dog can survive thyroid cancer. If caught early and treated adequately, thyroid cancer in dogs is manageable.

Surgery has the best outcome among all the treatments for thyroid cancer. If a dog’s tumor is small, hasn’t spread, and is loosely attached to the surrounding tissues, there is a very high chance of recovery.

However, even dogs that may not get rid of their thyroid cancer completely can go on to live relatively happy lives with the proper treatment.