Lymphoma in Cats

Lymphoma is one of the most common cancers diagnosed in cats. It is a cancer of the lymphocytes (a type of white blood cell) and is found throughout many areas of the body which include: lymph nodes, spleen, liver, gastrointestinal tract and bone marrow.

Unlike lymphoma in dogs, viral causes of feline lymphoma are well defined, and the feline leukemia virus (FeLV) has been shown to cause a significant (~60 fold) increase in risk for development of lymphoma in cats. We typically see lymphoma diagnosed in younger cats that are infected with the feline leukemia virus, and in older cats that are not infected with the virus. Other possible risk factors include exposure to second hand tobacco smoke, chronic immunosuppressive therapy, as well as chronic inflammatory diseases.

Types of Lymphoma

Lymphoma can be subdivided into several different forms which is dependent on location of the tumor. These locations can include:

Gastrointestinal Tract: The most common form is involvement of the gastrointestinal (GI) tract. This includes the stomach, intestines and liver; as well as some of the lymph nodes surrounding the intestines. Cats with this type of lymphoma often have clinical signs consisting of vomiting, diarrhea, weight loss or a decreased appetite.

Mediastinal: The mediastinum is a term used for a special aggregation of lymphoid tissue in the chest. Cats with this type of lymphoma are usually young and often seen because of a sudden onsent of difficulty breathing, decreased energy level and decrease in appetite.

Renal: The kidneys can be the primary sites of involvement. Cats that have this type are often seen because of signs related to kidney failure (increased thirst, increased urination, loss of appetite, vomiting).

Bone Marrow: If the cancer were confined to the bone marrow, it is considered leukemia. Most patients are presented to the hospital for a decrease in energy and appetite. Bloodwork, usually reveals a change in their red blood cell and white blood cell counts.

External Lymph Nodes: In a few cats, the only site of involvement is the external lymph nodes. These cats may be seen because of problems such as vomiting and loss of appetite or because the owner found “lumps” (enlarged lymph nodes) on their cat.

Other Sites: We will occasionally see other sites such as the skin, nose, brain and spinal cord as the primary site of involvement

Diagnosis and Initial Evaluation

A biopsy (tissue) or cytology (aspirate) sample is required in order to make a diagnosis of lymphoma. In some cases, we can obtain a diagnosis by a fine needle aspirate, but in other situations, a biopsy to obtain a larger piece of tissue is necessary to confirm the diagnosis. The ease with which a diagnosis can be obtained depends upon where the tumor is located.

The first step for any patient suspected of having lymphoma includes determining the extent of the disease which is known as staging. This includes a complete blood count (CBC), serum chemistry profile (which looks at things such as liver and kidney function, protein levels, blood sugar and electrolytes), urinalysis and FeLV/FIV testing are always recommended and provide important information regarding the effects of the cancer on body functions as well as the ability of the patient to handle chemotherapy or other treatments. Additional tests include chest radiographs, abdominal ultrasound along with possible bone marrow aspirate and CT/MRI. Once we determine the extent of disease, we can then decide on the best treatment for your pet.

Treatment and Prognosis

Chemotherapy is the mainstay of treatment for lymphoma; however, there may be situations when surgery and/or radiation are also indicated. Radiation therapy may be recommended if the cancer is localized to one site such as the nasal cavity. Specific recommendations will be discussed based on your pet’s particular situation.

Fortunately, lymphoma is very responsive to chemotherapy where 50-70% of treated cats will go into remission. The definition of remission is the complete disappearance of detectable cancer; however, microscopic amounts of tumor cells can remain hidden in the body. A remission is NOT a cure but it does allow your pet to experience a good quality of life without clinical signs associated with their disease. The length of the remission depends upon many factors including the primary site, how your pet is at the time of diagnosis and the extent of disease. In most situations, the median remission and survival times (with chemotherapy) are between six to twelve months; with 25% of cats experiencing disease control for greater than one year and approximately 10-15% of cats living longer than two years.

Solitary lymphoma such as nasal is generally treated with radiation +/-chemotherapy. The radiation can be considered definitive with the intent for long term control or palliative for symptom relief in order to
Improve and/or maintain the patient’s quality with minimal negative impact. The prognosis for solitary lymphoma such as nasal lymphoma is generally better with many cats achieving local control for 1-1.5 years although there is still a concern that the cancer may spread within 3-6 months. If solitary lymphoma is treated with radiation and the cancer progresses down the road, then chemotherapy can be considered at that time.

The exact chemotherapeutic drugs and schedule will depend upon how aggressively the cancer is behaving, how sick your pet is at the start of treatment, any abnormalities in organ function (particularly kidneys and liver), and the goals of treatment. Chemotherapy is most effective when we used a combination protocol; therefore, most protocols generally consist of 4-6 different drugs. This is called a multi-drug protocol. Multi-drug protocols most commonly include Elpsar (L’asparaginase), Vincristine (Oncovin), Cytoxan (Cyclophsophamide), Adriamycin (Doxorubicin) and Prednisone. Initially, treatments are given more frequently (i.e. once weekly) and then, depending upon the response and protocol used, are gradually spread out and/or discontinued. Other options for therapy may consist of using a single chemotherapy drug (single agent therapy) at 3- week intervals, or palliative care which is simply designed to keep your pet comfortable at home for as long as possible. Bloodwork and/or X-rays/ultrasounds are generally repeated at regular specified intervals to monitor for side effects (such as a low white blood cell count) and to determine the your pet’s response to treatment.

Side effects

Fortunately, most cats tolerate chemotherapy very well and experience minimal side effects. Serious side effects are only seen in 5% of the patients which require outpatient care and less than 1% will require hospitalization or experience any life threatening side effects. If side effects are serious or intolerable, we can consider either lowering the dose of the offending drug or substituting a different drug. Side effects include nausea, vomiting and loss of appetite, diarrhea, extreme tiredness or rarely infection. Certain chemotherapy agents can affect organ function over time, so close monitoring with bloodwork is recommended. Cats do not lose their hair but may lose their whiskers and have a different texture to their fur secondary to chemotherapy.


The ultimate goal of any treatment is to improve your pet’s quality of life and your oncologist will work with you to determine the treatment option that you feel most comfortable with.

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.