Canine Thyroid Carcinoma

At Animal Cancer Care Clinic (ACCC), we understand that discovering a lump in your dog’s neck and receiving a diagnosis of thyroid carcinoma can be a source of concern. Please know that our dedicated and compassionate team is here to support you and your furry companion every step of the way. Thyroid carcinoma is a relatively common endocrine cancer in dogs, and while it can be locally invasive and have the potential to spread, we have advanced diagnostic and treatment options available at ACCC aimed at managing the disease, addressing any associated complications, and maximizing your dog’s quality of life. Open communication with our veterinary team is crucial, and we encourage you to ask any questions you may have.

What is the Thyroid Gland and Thyroid Carcinoma?

The thyroid gland is a small, butterfly-shaped gland located in the neck, just below the larynx (voice box) and trachea (windpipe). It produces hormones (primarily thyroxine or T4, and triiodothyronine or T3) that regulate metabolism, energy levels, and various other bodily functions.

Thyroid carcinoma is a malignant tumor that arises from the cells of the thyroid gland. These tumors can vary in size and growth rate. They can be locally invasive, meaning they can grow into surrounding tissues in the neck, such as the trachea, esophagus, blood vessels, and nerves. They also have the potential to spread (metastasize) to other parts of the body, most commonly the regional lymph nodes (cervical lymph nodes in the neck) and the lungs. Less frequently, they can spread to bone or other organs.

Thyroid carcinoma is not typically associated with an overproduction of thyroid hormones (hyperthyroidism). Most dogs with thyroid carcinoma have normal to decreased thyroid hormone levels.

What Causes Thyroid Carcinoma in Dogs?

The exact cause of thyroid carcinoma in dogs is not fully understood. However, some factors are suspected to play a role:

Age: Thyroid carcinoma is more common in older dogs, typically over the age of 8-10 years.
Breed: Certain breeds, such as Boxers, Golden Retrievers, Beagles, and Siberian Huskies, appear to have a higher risk of developing thyroid tumors, suggesting a genetic predisposition.
Environmental Factors: Some studies have investigated potential environmental factors, but no definitive links have been established.
Previous Radiation Exposure: Prior radiation therapy to the neck area for other conditions may increase the risk of thyroid carcinoma.

Thyroid carcinoma is not contagious to other pets or humans.

Signs and Symptoms of Thyroid Carcinoma:

The signs and symptoms of thyroid carcinoma in dogs can vary depending on the size and location of the tumor and the extent of local invasion or metastasis:

Palpable Neck Mass: The most common presenting sign is a firm, often non-painful, swelling or lump that you or your veterinarian can feel in the neck area. These masses can vary in size and may grow over time.
Difficulty Swallowing (Dysphagia): If the tumor is large and invades the esophagus, it can make swallowing difficult.
Difficulty Breathing or Noisy Breathing (Stridor): If the tumor compresses or invades the trachea, it can lead to difficulty breathing or a harsh, noisy breathing sound.
Coughing: Compression or irritation of the trachea may also cause coughing.
Voice Change or Hoarseness: Invasion or compression of the larynx or nerves controlling the vocal cords can lead to a change in your dog’s bark.
Lethargy or Weakness: These more generalized signs may occur if the cancer is advanced or has metastasized.
Enlarged Lymph Nodes in the Neck: If the tumor has spread to the regional lymph nodes, you may notice enlarged lumps in the neck area.
Signs of Lung Metastasis: If the tumor has spread to the lungs, your dog may develop coughing, difficulty breathing, or exercise intolerance.

It’s important to note that other conditions can cause neck masses in dogs. Therefore, a thorough diagnostic workup is essential for an accurate diagnosis.

How is Thyroid Carcinoma Diagnosed?

Diagnosing thyroid carcinoma at Animal Cancer Care Clinic typically involves a combination of the following:

Physical Examination: Our veterinarians will perform a thorough physical examination, paying close attention to the neck area and palpating for any masses or enlarged lymph nodes.
Fine Needle Aspirate (FNA): An FNA of the neck mass can often provide a preliminary diagnosis by identifying cancerous cells. However, FNA alone may not always be definitive in differentiating between different types of thyroid tumors (benign vs. malignant) or in determining the extent of invasion.
Biopsy: A surgical biopsy, where a larger tissue sample is obtained, is usually recommended for a definitive diagnosis and to assess the type and grade of the tumor. The biopsy can be obtained through a small surgical incision or during the surgical removal of the tumor.
Blood Work: A complete blood count (CBC) and serum chemistry panel are typically performed to assess your dog’s overall health and to measure thyroid hormone levels (T4 and free T4). As mentioned earlier, most dogs with thyroid carcinoma have normal thyroid function.
Imaging (Radiographs/X-rays, Ultrasound, CT Scan): Imaging studies are crucial for evaluating the local extent of the tumor, assessing for invasion into surrounding structures, and checking for metastasis.
- Neck Ultrasound: Ultrasound can help visualize the thyroid mass, assess its size and relationship to nearby structures, and guide FNA or biopsy procedures.
- Chest Radiographs or CT Scan of the Chest: To check for metastasis to the lungs.
- CT Scan of the Neck: A CT scan of the neck may be a valuable imaging modality for assessing the size and extent of the primary tumor and its invasion into surrounding tissues, as well as evaluating the regional lymph nodes.

Treatment Options for Canine Thyroid Carcinoma:

At Animal Cancer Care Clinic, our treatment approach for thyroid carcinoma is tailored to the size and extent of the tumor, the presence of metastasis, and your dog’s overall health. Treatment options may include:

Surgery: Surgical removal of the thyroid tumor is often the primary treatment of choice, especially for smaller, mobile tumors without evidence of extensive local invasion or distant metastasis. Our skilled surgeons at ACCCare experienced in performing thyroidectomy (removal of the thyroid gland). The extent of surgery will depend on the size and invasiveness of the tumor.
Radiation Therapy: Radiation therapy can be used as an adjuvant (additional) treatment after surgery to address any remaining microscopic disease in the neck area. It can also be used as the primary treatment for tumors that are not surgically resectable or for palliation (to shrink the tumor and alleviate symptoms). We can discuss if radiation therapy is a suitable option for your dog.
Chemotherapy: Chemotherapy may be recommended for dogs with thyroid carcinoma that has spread to distant sites (metastasis) or for aggressive tumors with a high risk of metastasis. Various chemotherapy protocols are available, and our veterinary oncologists at ACCC will develop a personalized plan for your dog.
Radioactive Iodine (I-131) Therapy (Less Common in Standard Practice for Carcinoma): Radioactive iodine therapy is a common and effective treatment for hyperthyroidism in cats (a benign condition). However, its use for thyroid carcinoma in dogs is less common and typically reserved for specific types of thyroid cancer (e.g. functional tumors producing excess hormone, which is rare in carcinoma) or in specialized centers.
Tyrosine Kinase Inhibitors (TKIs): In some cases, TKIs may be considered as a treatment option, particularly for tumors that are not amenable to surgery or radiation therapy, or for metastatic disease. TKIs, such as Palladia, can also be used to try to shrink tumors to make surgery an option.
Palliative Care: For dogs with advanced disease where curative treatment is not feasible, palliative care focuses on managing symptoms, such as pain or difficulty breathing, and maintaining the best possible quality of life.

What to Expect During and After Treatment:

If your dog undergoes treatment for thyroid carcinoma at Animal Cancer Care Clinic, you can expect:

Close Monitoring: Our team will closely monitor your dog’s recovery after surgery and their response to any other treatments, including regular physical examinations and potentially blood work and imaging.
Post-Surgical Care: Following surgery, we will provide detailed instructions for post-operative care and pain management. We will also monitor for any complications such as hypocalcemia (low calcium levels due to parathyroid gland disturbance) or Horner’s syndrome (nerve damage).
Management of Potential Side Effects: We will proactively manage any potential side effects associated with radiation therapy or chemotherapy.
Regular Follow-Up Appointments: These appointments will involve physical examinations, palpation of the neck, and potentially repeat imaging studies (neck ultrasound, chest radiographs or CT scans) to monitor for recurrence or metastasis.

Prognosis for Canine Thyroid Carcinoma:

The prognosis for dogs with thyroid carcinoma can vary depending on several factors, including:

Size and Mobility of the Tumor: Smaller, freely movable tumors that can be completely removed surgically generally have a better prognosis.
Local Invasiveness: Tumors that are extensively invasive into surrounding neck structures are more challenging to treat and may have a less favorable prognosis.
Presence of Metastasis: Dogs with metastasis to regional lymph nodes or distant organs at the time of diagnosis have a less favorable prognosis.
Histologic Grade and Type of Tumor: Some types of thyroid carcinoma are more aggressive than others.
Completeness of Surgical Removal: Achieving clean surgical margins is important for local control.
Response to Adjuvant Therapy: The use of radiation therapy or chemotherapy after surgery can impact the prognosis.

With complete surgical removal of a small, mobile tumor, some dogs can have survival times of several years. However, for larger, invasive tumors or those with metastasis, the prognosis is generally more guarded. Multi-modal therapy, combining surgery with radiation therapy and/or chemotherapy, may improve outcomes in some cases.

We will discuss the potential prognosis for your dog based on their individual circumstances and the chosen treatment plan at ACCC. Our goal is to provide realistic expectations while focusing on maximizing their comfort and quality of life for as long as possible.

Coping with a Thyroid Carcinoma Diagnosis:

Receiving a diagnosis of thyroid carcinoma for your dog can be a source of worry and uncertainty. Please know that the team at ACCC is here to offer not only the best possible medical care for your dog but also compassionate support for you and your family during this time.

We encourage you to ask us any questions you have and to share your feelings and concerns openly. We want you to feel informed and supported as you make important decisions about your dog’s care.

Our commitment is to work with you to develop a treatment plan that is tailored to your dog’s needs and your wishes, while always prioritizing their comfort and well-being.

Questions to Ask Your Veterinarian:

To help you better understand your dog’s condition and the treatment options available, here are some questions you may find helpful to ask us:

What is the size and location of my dog’s thyroid tumor?
Has the tumor invaded surrounding tissues in the neck?
Have the regional lymph nodes been evaluated for metastasis? What were the findings?
Has the cancer spread to other parts of the body? If so, where?
What are the treatment options available for my dog’s thyroid carcinoma?
What are the goals of each treatment option (e.g., local control, preventing metastasis, extending survival)?
What are the potential side effects of the recommended treatment plan? How will these be managed?
What is the expected prognosis for my dog with the recommended treatment?
How will my dog’s comfort and quality of life be maintained?
What is the estimated cost of the recommended treatment plan and ongoing care?
What can I do at home to best support my dog during this time?

Conclusion:

At Animal Cancer Care Clinic, we are dedicated to providing compassionate and comprehensive care for dogs with thyroid carcinoma. Our experienced team will work closely with you to develop a personalized treatment plan focused on managing the disease and maximizing your dog’s quality of life. Please do not hesitate to reach out to us with any questions or concerns you may have. We are here to support you and your cherished canine companion through this challenging journey.