Thyroid Tumors in Dogs

Thyroid tumors comprise 1.2-3.8% of all tumors in dogs and the majority (about 90%) are found to be malignant (known as thyroid carcinoma or thyroid adenocarcinoma). Breeds that have a higher risk of developing this type of cancer include Beagles, Boxers and Golden Retrievers although any dog can develop a thyroid tumor. Most dogs with thyroid tumors are older (>10 years).

Clinical signs

The most common sign is the finding of a mass in the neck. In most cases, these tumors are present on only on one side of the neck (unilateral) but there is a small percentage of dogs who around found to have cancer in both thyroid glands (bilateral). If the mass grows large enough, it could cause clinical signs which may include coughing, difficulty breathing or swallowing and rarely swelling in the face.

The majority of these tumors are considered to be non-functional (this means that they are not producing any thyroid hormone). Some dogs with this type of cancer are actually hypothyroid (have low levels of thyroid hormone). If the tumor is producing thyroid hormone, dogs can have signs of hyperthyroidism, which can include drinking and urinating more, weight
loss, increased panting and restlessness.


A diagnosis of a thyroid tumor can be made either by a needle aspirate or biopsy. These tumors often have a very well developed blood supply which means that an incisional biopsy (only taking a small piece of the mass) can be challenging and is not recommended due to the high risk of bleeding.
Not only can thyroid tumors be locally aggressive and invade into surrounding tissues as it grows, but up to 35% of patients have evidence of metastasis at the time of diagnosis. The most common sites of metastasis include the local lymph nodes and lungs. To assess the extent of disease, staging tests are recommended and include:

  • Chest radiographs determine if there is any evidence of disease in the lungs.
  • Blood work is recommended and consists of a CBC (which checks the red and white blood cells and platelets), a chemistry panel to look at organ function, a urinalysis and a thyroid level.
  • If surgery is going to be considered, a CT scan of the neck (and possible the chest) may be recommended as the next step after staging to help determine whether or not surgery will be successful and look a little closer for any evidence of metastasis. CT image shows large thyroid tumor (arrows).



Surgery is the treatment of choice whenever possible. Removal of these tumors can be complicated given the well developed blood supply and the fact that these tumors surround vital structures such as the esophagus and trachea. Whether surgery alone is enough or if radiation therapy and chemotherapy will be needed following surgery depends on the size and invasiveness of the tumor as well as the final biopsy report. Size of the tumor and invasiveness are predictors of outcome. Smaller tumors that are freely movable carry a better prognosis than larger or fixed thyroid tumors.

Radiation therapy

There are two different ways that radiation therapy can be used. The decision about what type of radiation therapy would be best is based on a number of different factors and the radiation oncologists recommendations.

For those dogs where the tumor can be removed but there are still tumor cells that remain at the surgical site, full course radiation therapy may be recommended. This type of radiation therapy involves the use of 15-20 treatments which is administered Monday through Friday for 3-4 consecutive weeks.

For those dogs whose tumors cannot be removed, we can consider using full course radiation therapy as described above although our ability to control the tumor is not as good due to the larger amount of tumor that needs to be treated.

For dogs that have tumors that cannot be removed, we can also consider a modified schedule of radiation therapy called palliative radiation therapy. This is a less intensive course of radiation therapy with fewer side effects but the trade-off is that it is not expected to control tumors for as long. Rather the goal of palliative radiation therapy is to focus on the patient’s quality of life. This type of radiation therapy involves the use of 3-4 treatments of radiation therapy with treatments being given at weekly intervals (ie. once weekly for 3-4 consecutive weeks).


Chemotherapy is frequently recommended due to the potential for metastatic disease, however, the treatment outcome is difficult to predict. Chemotherapy is most often discussed for tumors that cannot be removed, tumors that are larger than 3 cm, and/or tumors where there is invasion into the blood vessels or evidence of metastasis. Dogs that already have spread to the lungs at the time of diagnosis may also benefit from
chemotherapy. Chemotherapy is typically not used alone but is most often combined with surgery and radiation therapy.

  • The most commonly used drugs for this type of cancer are Palladia, Adriamycin (doxorubicin) and Carboplatin.
  • Doxorubicin and carboplatin are administered intravenously as an outpatient once every 3 weeks for a total of 4-6 treatments when combined with surgery. Palladia is an oral chemotherapy agent that is administered at home. Fortunately, the risk for side effects from chemotherapy is low and can include stomach upset (decrease in appetite, nausea, vomiting, diarrhea and/or lethargy), decrease in white blood cell counts and possible thinning of fur coat. Less than 10% of patients will need to come in to the hospital for outpatient care due to chemotherapy side effects and less than 1% will require hospitalization or experience any life threatening side effects.
  • The goal of chemotherapy is to help improve your pets quality of life and we will work with you to achieve this goal.

Radioactive iodine

Radioactive iodine has been used for the treatment of thyroid tumors in dogs although it is not commonly used due to technical issues. There are currently only a few facilities in the USA that are able to treat dogs with radioactive iodine so patients need to travel to one of these facilities. In addition, due to the doses that are needed for treatment, patients may need to remain in isolation for several weeks following treatment which makes this type of a treatment less practical.


The prognosis with treatment depends partly on the size of the tumor and whether or not the tumor is freely movable or is fixed to the underlying structures. The prognosis is also influenced by the rate of growth of the tumor as we sometimes see tumors that are very slow to progress even in advanced stages.

For tumors that are small and freely movable, the prognosis with surgery alone is considered to be good with a median survival time of 2 years.

Larger tumors that can still be removed by surgery may require radiation therapy and/or chemotherapy after surgery. The survival time of these patients may not be as long but in our experience, the median survival time is 18-24 months with combination treatment.

For tumors that cannot be removed, the recommended treatment would be radiation therapy (either full course or palliative radiation therapy) AND chemotherapy. Dogs that fall into this category can experience survival times of 6-12 months.

Thyroid carcinoma is not usually a cancer that is curable, but with treatment, can be controlled while maintaining your pet’s good quality of life. Your oncologist will be able to discuss the treatment options, prognosis and help guide you as to the most appropriate plan for your beloved family member.

Recognizing the Important Work of Service Dogs

Service dogs are special companions. They help people with disabilities, they provide comfort in times of crisis, they support our country’s police force and military, and they do so much more. At Atlantic Veterinary Internal Medicine & Oncology, we understand just how important these dogs are, especially to the people they serve. We’re proud to be able to provide internal medicine and oncology services to keep them in the best of health so they can go on to do great things.

So, what are some of those great things service dogs do? Not all service dogs wear a vest, meaning many of them are doing extraordinary work in plain sight. Let’s take a look today at the essential roles service dogs play in our communities, and how they help their human companions.

What Kinds of Service Dogs Are There?

To understand what service dogs do, it’s first important to understand what they are. The Americans with Disabilities Act (ADA) defines service dogs as dogs that are individually trained to perform specific tasks and to work with people with disabilities. The ADA defines disabilities as “physical, sensory, psychiatric, intellectual, or other mental disability.” It’s important that the work of the service dog be directly related to the handler’s disability, which grants them status as an official service dog. Service dogs have legal rights that other trained dogs don’t have including full public access rights with their handler and acceptance on flights and other forms of public transport.


Types of service dogs include:
Guide Dogs – Guide dogs, or “seeing eye” dogs are one of the most well-known type of service dog. These dogs help people with blindness or visual impairment navigate the world safely and independently.

Hearing Dogs – Hearing dogs alert people who are deaf to sounds such as an alarm, a knock on the door, or someone entering a room.

Psychiatric services dogs – Psychiatric dogs assist people living with a mental disorder such as post-traumatic stress disorder, anxiety, or depression. These dogs can help lessen the frequency of psychiatric episodes and can help their humans feel safer in the world. Those with PTSD can often be hyper vigilant about their safety, but their dogs can help them feel safer by entering a room before them and turning on the light, accompanying them to public places, and more.

Mobility assistance dogs – These dogs help people with mobility limitations, such as needing to use a wheelchair, prosthetic, or other assistive device. Mobility assistance dogs perform tasks for their people such as fetching things their handlers can’t reach, opening doors or cabinets, and carrying items.

Seizure alert/response dogs – While somewhat controversial, seizure alert dogs are trained to predict the onset of a seizure in their handlers, although there is no clear scientific evidence that they can do this reliably every time. Seizure response dogs, on the other hand, are trained to stand guard over their handler when they are experiencing a seizure, bring them medication or a phone after an episode, or even go for help.

Autism assistance dogs – These dogs help those on the autism spectrum more easily navigate their surroundings. They can help distinguish important sensory input (like a smoke alarm) from other sensory input, act as icebreakers in social situations, and can even alert their handlers to repetitious behaviors or overstimulation.

What’s the Difference Between Service Dogs & Working Dogs?

Working dogs are those that are trained for a specific purpose such as detection, herding, hunting, search and rescue, police work, or military service. These dogs do not have the same legal rights as service dogs because they are not assisting someone with a disability—therefore they are not covered under the ADA. However, whenever and wherever they are performing their job, they are not often subject to legal ramification.

Types of working dogs include, but are not limited to:
Search and rescue – these dogs are trained to find missing persons, whether from a kidnapping, a natural disaster, drowning situations, avalanches, or other dire situations. They often either use a scent in the air or the scent of a specific object to find what or whom they’re looking for.
Police K9 units – These dogs have a variety of roles in the police department from sniffing out drugs, criminals in hiding, or contraband to patrolling, or actively attacking a suspect.
Military dogs – Military dogs serve with our armed forces in many different roles similar to police dogs, but the ante is upped significantly. These dogs are trained to endure harrowing combat experiences while still performing their duties, which might include explosive detection, patrol, search and rescue, and attack.

Are Therapy Dogs Considered Service Dogs?

Therapy dogs are not considered service dogs. While therapy dogs do go through training to become certified, they are not trained in a specific role to help someone with a disability, and so are not covered by the ADA. Therapy dogs often work with their owner to provide comfort to people in nursing homes, hospitals, hospices, schools, and mental institutions. These dogs need to be comfortable in new environments and unfazed by unfamiliar sounds and movements. They also need to be happy with being handled and loving people is a huge plus!

We Support Working & Service Dogs

At Atlantic Veterinary Internal Medicine & Oncology, we are proud to provide services to our community’s working and service dogs that help them do their best jobs yet. These dogs must be at the peak of physical fitness to be able to fully perform their duties and serve their handlers. We also recognize the deep bond these dogs share with their handlers, and we’re dedicated to strengthening it with our specialized medical care. If you or a loved one works with a service or working dog who needs internal medicine or oncology care, please reach out to us at (410) 224-0121 and we’ll be happy to help.

Understanding Osteosarcoma in Dogs in Annapolis, Columbia & Towson

Osteosarcoma is a form of bone cancer in dogs that accounts for 85% of primary bone tumors diagnosed, making it the most common bone tumor. It is a highly aggressive tumor, characterized by local invasion and destruction of the bone as well as early metastasis (spread to other organs, the most common site of metastasis being the lungs). Osteosarcoma most commonly affects the limbs (or the appendicular skeleton) of large to giant breed dogs.  It can also occur in other bones such as the skull, ribs, vertebrae, and pelvis (the axial skeleton) which are more common sites in smaller dogs.

Clinical Signs of Osteosarcoma

The signs associated with bone cancer in dogs may be nonspecific and depend on the location. Tumors involving the limbs often cause various degrees of lameness, pain, and muscle wasting, and a firm swelling may become evident as the tumor grows. The pain can cause other problems such as irritability, aggression, loss of appetite, weight loss, whimpering, restlessness or reluctance to exercise.

Diagnosis and Work-up (Staging)

The initial evaluation for any dog suspected of having a bone tumor will include a complete physical exam, blood work (complete blood count, serum chemistry profile), urinalysis, radiographs of the primary site as well as the lungs, and an aspirate or biopsy of the lesion. In some cases a CT scan is recommended to evaluate for metastasis and/or surgical planning.  Unfortunately, 80-90% of dogs diagnosed with osteosarcoma already have microscopic spread to the lungs but we are not able to detect these microscopic lesions with X-rays or a CT scan. The work-up and staging are important for two reasons. First, it is necessary to determine the tumor type and extent of the cancer to determine the appropriate treatment and prognosis. Secondly, it also provides the clinician with information regarding your dog’s general health and may identify concurrent medical or musculoskeletal problems all of which may influence the treatment recommendations. 

Treatment Options for Osteosarcoma in Dogs

Treatment recommendations for bone tumors depend on multiple factors and the ultimate goal is to help improve your pet’s quality of life. Treatment can be divided into two parts:

  • Pain management/treatment of the primary tumor
  • Treatment to address the risk for metastatic disease

Pain Management

The initial focus of treatment is pain management. Osteosarcoma causes pain due to the invasion and destruction of normal bone by the tumor. There are several options for pain management depending on the location of the tumor. These include surgery (amputation for osteosarcoma of the limb), oral analgesics (pain relievers), radiation therapy and/or intravenous bisphosphonate therapy. 

For osteosarcoma involving a limb, amputation is the best method for pain control. It is much easier to control post-operative pain than it is to control chronic bone pain. An amputation also eliminates the risk of a fracture at the tumor site. Fractures occur because the tumor weakens the bone to the point that it can break. Fortunately, the risk of a fracture is low (~20%).  Most dogs will do very well with an amputation and often resume many of their normal activities such as running, playing, swimming, etc. It is important to understand that if an amputation is performed for osteosarcoma without chemotherapy, most patients develop metastatic disease and succumb to the cancer within 4-6 months, which is why we don’t always recommend amputation as a sole therapy.

For dogs that are not candidates for an amputation or situations in which a caretaker isn’t interested in amputation, we have several options for pain management that can be used singly or in combination. There is no “one size fits all” when it comes to pain management and we may need to try several combinations until we find what works best for a particular dog. 

Oral Analgesics include non-steroidal anti-inflammatory drugs (NSAIDS) (or aspirin-like drugs), steroids and narcotics. It is common to combine a NSAID with a pain medication like gabapentin, amantadine, codeine and fentanyl.

Palliative Radiation Therapy (PRT) involves the use of several large doses of radiation administered once a week, for 3-4 doses. PRT appears to be the best option for pain management if surgery (amputation) is not pursued. The goal of this form of radiation is to improve/maintain the patient’s quality of life with minimal negative impact (minimal side effects). Approximately 70% of dogs experience pain relief with PRT which lasts for an average of 4 months. It may be possible to repeat a course of PRT, depending on the dog, though the duration of the response is usually shorter than the original response. PRT for bone tumors (appendicular) is for pain management and is not a treatment for the primary tumor. In most patients the tumor continues to progress even though the patient is more comfortable and fracture is still a risk.

Bisphosphonates: Bisphosphonatesare is a class of drugs that are meant to slow or prevent bone breakdown as well as increase bone production. This class of drugs is used frequently in women to prevent osteoporosis (ie. Boniva or Fosamax). Several of the drugs have also been used to help control pain from bone destruction. The most commonly used drug is zoledronate. This medication is administered intravenously once every 4 weeks as a 15 minute infusion. Initially we plan 2-3 treatments and then determine if there has been an improvement. If there has been an improvement, this drug can be repeated for as long as there is response and the patient tolerates the drug. Side effects are rare, but we do monitor kidney function prior to each treatment due to a low risk for kidney damage.


The most common cause of death in dogs with appendicular osteosarcoma, especially those undergoing an amputation, is metastasis to the lungs. Because of this, systemic chemotherapy is recommended as a follow-up to surgery for dogs with appendicular osteosarcoma. Chemotherapy is not likely to cure most dogs with osteosarcoma but can significantly prolong their quality of life to 10-12 months on average with 20% of patients alive at 2 years. Survival time for dogs treated with an amputation alone is about four months. We currently recommend the chemotherapy drug Carboplatin. This chemotherapy agent is administered intravenously once every three weeks for 6 doses. Most dogs tolerate chemotherapy well with less than 10% experiencing side effects significant enough to warrant an outpatient visit and less than 1% will require hospitalization or experience any life-threatening side effects secondary to chemotherapy.  

The goal of any treatment is to maintain your pet’s quality of life. Your veterinarian will work with you to determine the best course of treatment for you and your dog.