Lymphoma in Dogs and Cats: Everything you need to know

A complete pet owner guide to signs, causes, diagnosis, stages, treatment, home care and prognosis

Written by:
Moses Chang
Posted on: August 13, 2026

Key symptoms	Enlarged lymph nodes, weight loss, vomiting, diarrhea, decreased appetite, tiredness, increased drinking/urination, breathing problems, and signs related to the affected organ.
Commonality	One of the most common cancers in dogs and cats, more common in middle-aged to older pets.
Transmission	Not contagious
Impact on health	Moderate to severe depending on the type and grade of lymphoma.
Treatment cost	Costs vary greatly depending on the type of lymphoma, diagnostic testing, treatment protocol, and duration of treatment.
Treatment duration	Depends on the type of lymphoma and treatment chosen. Some treatments are given over several months, while some forms require longer-term medication.
Ease of prevention	Low to moderate.

Most affected dog breeds

Golden Retriever
Boxer, Rottweiler
Basset Hound
Bull Terrier
Scottish Terrier
West Highland White Terrier
Yorkshire Terrier
Chow Chow
Saint Bernard
German Shepherd
Beagle
Poodle
Bullmastiff
Bulldog

Most affected cat breeds

One day your dog or cat may seem perfectly healthy. Then, a few days later, you notice a lump under their jaw, they stop eating, or they seem much more tired than usual. Hearing that your pet has lymphoma can be frightening. Lymphoma is one of the most common cancers seen in dogs and cats. The good news is that it is also one of the cancers that can often respond well to treatment. ¹ ²

Without treatment, aggressive lymphoma can make a pet very sick in a short amount of time. With treatment, however, many pets can have months or even years of good-quality life, depending on the type of lymphoma, where it is located, and how well it responds to treatment. ¹ ²

This guide explains what lymphoma is, why some pets are more likely to develop it, what signs to look for, how veterinarians diagnose it, and what treatment options are available.

What is Lymphoma?

Lymphoma, sometimes called lymphosarcoma, is a type of cancer that affects lymphocytes. Lymphocytes are a type of white blood cell. They are an important part of the immune system, which protects your pet from infections and other diseases.

Lymphocytes normally live and travel through many parts of the body, including:

Lymph nodes
Spleen
Bone marrow
Thymus
Intestinal and other lymphoid tissues
Because lymphocytes are found throughout the body, lymphoma can develop in many different organs. When a lymphocyte becomes cancerous, it starts growing and dividing when it should not. The abnormal cells can build up in large numbers and begin to replace healthy cells. They can also spread to other parts of the body and interfere with normal organ function. ¹ ²

How does the Lymphatic System work?

To understand lymphoma, it helps to understand the lymphatic system. Think of the lymphatic system as a large network of roads that helps your pet’s body find and fight disease. Lymphocytes normally move through this system looking for things that could make your pet sick. With lymphoma, some of these cells become cancerous. Instead of growing in a controlled way, they multiply too much and form collections of abnormal cells. ¹ ²

B-Cell vs. T-Cell Lymphoma

Not all lymphoma is the same. There are two major types of lymphocytes involved in lymphoma:

B-cells
T-cells

Veterinarians can perform special tests to find out which type of lymphoma your pet has. This is called immunophenotyping. Knowing whether the cancer is B-cell or T-cell is important because the two types can behave differently and may have different responses to treatment. ²

1. B-cell lymphoma

B-cell lymphoma generally has a better outlook in dogs than T-cell lymphoma. Dogs with B-cell lymphoma treated with chemotherapy often have longer survival times than dogs with T-cell lymphoma. ¹ ²

2. T-cell lymphoma

T-cell lymphoma can be more aggressive and is generally associated with a shorter survival time in dogs. ¹ ²

This is one reason your veterinarian may recommend additional testing after lymphoma is diagnosed. Knowing the type of lymphoma can help the veterinary team better understand what to expect and choose an appropriate treatment plan.

High-grade vs. low-grade Lymphoma

Veterinarians may also describe lymphoma based on how quickly the cancer cells grow.

High-grade lymphoma

High-grade lymphoma grows quickly. Pets with high-grade lymphoma may become sick quite suddenly, but these cancers can also respond well to chemotherapy. Many canine lymphomas are high-grade cancers. ¹ ²

Low-grade lymphoma

Low-grade lymphoma grows more slowly. Some pets with low-grade lymphoma may have few obvious signs for a long time. In dogs, low-grade lymphoma can sometimes be associated with survival times of more than two years when appropriately treated. ¹ Cats commonly develop a slow-growing type of intestinal lymphoma called small-cell lymphoma. This form behaves differently from the faster-growing large-cell lymphoma. ³

Dogs and cats get different types of Lymphoma

Although dogs and cats can both develop lymphoma, the disease does not always look the same in the two species.

Lymphoma in Dogs

In dogs, the most common form is called multicentric lymphoma. This means that several lymph nodes around the body become affected. About 80–85% of canine lymphoma cases are multicentric. ¹ ²

Owners may notice enlarged lymph nodes:

Under the jaw
In front of the shoulders
Behind the knees
In other areas of the body

These lymph nodes are usually firm but not painful. Lymphoma can also affect other parts of a dog’s body, including the intestines, skin, chest, kidneys, eyes, nervous system, liver, and bones. ¹ ²

Lymphoma in Cats

Cats commonly develop lymphoma in the gastrointestinal (GI) tract, meaning the stomach and intestines. This can make feline lymphoma harder for owners to notice.

Instead of obvious lumps under the skin, a cat may develop:

Weight loss
Vomiting
Diarrhea
Changes in appetite
Other digestive problems

Gastrointestinal lymphoma is now the most common form of lymphoma seen in many cats, particularly older cats that are FeLV-negative. ¹ ⁴

What causes Lymphoma and which pets are at risk?

Unfortunately, there is usually no single reason why a pet develops lymphoma. The exact cause is not completely understood. Scientists believe lymphoma develops from a combination of genetic and environmental factors that cause lymphocytes to grow abnormally. ¹ ²

Possible risk factors include:

Genetics
Age
Viruses
Long-term inflammation
Certain environmental exposures

Having one of these risk factors does not mean that a pet will definitely get lymphoma. Many pets with lymphoma have no obvious risk factor at all.

1. Genetics

Some dogs seem to be more likely to develop lymphoma because of their genetics.

Studies have found that certain breeds have a higher risk of lymphoma than others. These include:

Golden Retrievers
Boxers
Rottweilers
Basset Hounds
Bull Terriers
Scottish Terriers
Bullmastiffs
Bulldogs
Beagles
German Shepherds
Saint Bernards
Other breeds and mixed-breed dogs

The exact risk can vary between studies and locations. For example, one large Australian study found increased lymphoma risk in several breeds, including Boxers, Bullmastiffs, Golden Retrievers, Rottweilers, Basset Hounds, Beagles, Bull Terriers, and Scottish Terriers. ⁵

This does not mean that these breeds will definitely develop lymphoma. It simply means that their risk may be higher than that of some other dogs.

2. Age

Lymphoma can happen at almost any age, but it is much more common in middle-aged and older pets. In dogs, lymphoma is most often diagnosed around 6–9 years of age. In cats, it is most often diagnosed around 10–12 years of age. ¹

Very young animals can still develop lymphoma, but this is much less common.

3. Viruses and Lymphoma in Cats

Viruses are especially important when talking about lymphoma in cats.

A. Feline Leukemia Virus (FeLV)

Feline leukemia virus (FeLV) is one of the most important known risk factors for lymphoma in cats. FeLV can affect a cat’s immune system and can increase the chance of certain cancers developing. Cats infected with FeLV have historically had a much higher risk of developing lymphoma than cats that are not infected. ²

Thankfully, FeLV has become less common in many cat populations because of testing, prevention, and vaccination. As FeLV has become less common, the types of lymphoma seen in cats have also changed. Gastrointestinal lymphoma is now the most common form of feline lymphoma, while mediastinal lymphoma was more common in the past. ²

B. Feline Immunodeficiency Virus (FIV)

Feline immunodeficiency virus (FIV) can also increase the risk of lymphoma. FIV affects the immune system, making it harder for the body to protect itself. However, the connection between FIV and lymphoma is not as strong as the connection with FeLV. ²

It is important to remember that having FeLV or FIV does not mean a cat will definitely develop lymphoma.

4. Chronic Inflammation

Long-term inflammation may also play a role in some types of lymphoma, especially intestinal lymphoma in cats. For example, cats with long-lasting inflammation of the intestines, such as inflammatory bowel disease (IBD), may have a higher chance of developing certain types of low-grade intestinal lymphoma. ¹

This does not mean that every cat with IBD will develop lymphoma. Most will not. Instead, ongoing inflammation is one possible factor that may contribute to the development of the disease.

5. Environmental factors

Researchers have also studied whether certain chemicals and environmental exposures might increase the risk of lymphoma in dogs. Possible risk factors that have been investigated include:

Certain herbicides
Lawn-care chemicals
Industrial chemicals
Other environmental pollutants
Strong magnetic or electromagnetic fields

Some studies have found links between certain chemical exposures and canine lymphoma. However, this does not prove that these exposures directly cause lymphoma in every dog. More research is needed to understand exactly how environmental factors may affect cancer risk. ¹ ⁶

What are the signs and symptoms of Lymphoma in pets?

The signs of lymphoma depend heavily on where the cancer is located. Some pets become obviously sick, while others may seem almost completely normal at first.

Dogs with lymphoma may develop:

Enlarged lymph nodes
Weight loss
Reduced appetite
Tiredness
Weakness
Vomiting
Diarrhea
Increased thirst or urination
Difficulty breathing
Abdominal swelling
Fever

The most classic sign of multicentric lymphoma is painless enlargement of multiple lymph nodes. ¹ ²

Cats can be more difficult to diagnose because their signs are often less obvious.

Possible signs include:

Weight loss
Poor appetite
Vomiting
Diarrhea
Tiredness
Increased thirst
Increased urination
Difficulty breathing
Sneezing
Nasal discharge
Abdominal swelling
Enlarged lymph nodes

Older cats with unexplained weight loss should be examined by a veterinarian because several serious diseases, including lymphoma, can cause this sign. ¹ ¹

How is Lymphoma diagnosed?

A veterinarian cannot diagnose lymphoma based only on symptoms. A proper diagnosis usually requires looking at the actual cells or tissue from the affected area. ¹

Fine-Needle Aspiration (FNA)

If a lymph node is enlarged, the veterinarian may perform a fine-needle aspiration (FNA). This involves placing a small needle into the lymph node and collecting some cells. The sample is then examined under a microscope.

FNA is:

Quick
Relatively inexpensive
Minimally invasive

Biopsy

Sometimes an FNA does not provide enough information. In these cases, the veterinarian may recommend a biopsy. A biopsy removes a larger piece of tissue so a pathologist can examine how the cells are arranged.

Biopsies can help determine:

The exact type of lymphoma
How aggressive it is
Whether it is low-grade or high-grade

Once lymphoma has been diagnosed, additional tests may be recommended to determine whether it is B-cell or T-cell lymphoma. As mentioned earlier, this is called immunophenotyping.

Tests that may be used include:

Flow cytometry
Immunohistochemistry
PARR (PCR for antigen receptor rearrangement)

Immunophenotyping helps predict how the cancer may behave. In dogs, B-cell lymphoma generally has a better response to chemotherapy and a longer average survival time than T-cell lymphoma. ¹ ² For dogs with multicentric B-cell lymphoma treated with CHOP chemotherapy, many achieve remission and have a medial survival is approximately 12–14 months. For T-cell lymphoma, average survival is generally shorter. ¹

Staging Lymphoma

Veterinarians may also perform tests to determine how far the cancer has spread. This is called staging.

Possible tests include:

Chest X-rays
Abdominal ultrasound
Blood tests
Lymph node sampling
Bone marrow testing

Lymphoma in dogs and cats is commonly divided into five stages based on how much of the body is affected.

The 5 stages are:

Stage I: One area or lymph node is affected
Stage II: Multiple lymph nodes in one general area are affected
Stage III: Lymph nodes throughout the body are affected
Stage IV: The liver or spleen is involved
Stage V: The blood, bone marrow, or nervous system is involved

There are also substage A and B classifications.

Substage A: The pet feels generally well.
Substage B: The pet is showing signs of illness. ¹

The stage can help veterinarians understand the disease and estimate prognosis, but stage alone does not determine the outcome.

How is Lymphoma treated?

Treatment may include chemotherapy, radiation therapy, surgery, steroids, or supportive care. ¹ ²

Chemotherapy

Chemotherapy is the main treatment for many forms of lymphoma. This may sound frightening, but chemotherapy is different for pets than it is for people. The goal of veterinary chemotherapy is usually to control the cancer while maintaining a good quality of life.

Most pets do not become severely sick from chemotherapy, and many continue eating, playing, and enjoying normal activities during treatment. ¹ ²

One of the most commonly used chemotherapy plans for dogs with multicentric lymphoma is called CHOP. CHOP is named after four chemotherapy drugs:

C: Cyclophosphamide
H: Hydroxydaunorubicin (doxorubicin)
O: Oncovin (vincristine)
P: Prednisone

For dogs with B-cell multicentric lymphoma, CHOP-based treatment can produce remission in approximately 80–95% of cases. Median survival is commonly around 12–14 months, although individual outcomes vary greatly. T-cell lymphoma generally has a shorter average survival time, often around 5–8 months, depending on the specific type and treatment. ¹

Cats can also receive chemotherapy for lymphoma. For cats with small-cell intestinal lymphoma, oral medications such as chlorambucil and prednisolone are commonly used, but stronger multi-drug chemotherapies may be recommended for more aggressive lymphoma. ¹

Veterinary chemotherapy is usually designed to control cancer while keeping side effects manageable. Most side effects are mild and temporary, although serious side effects can occasionally occur. ¹

Steroids

Prednisone or prednisolone may be used as part of lymphoma treatment. Steroids can reduce inflammation, improve appetite, make a pet feel better, and even temporarily shrink lymphoma. ¹

However, steroids alone usually do not provide the same long-term control as a full chemotherapy protocol. If chemotherapy is being considered, veterinarians may recommend discussing steroid use first because giving steroids before certain chemotherapy drugs can sometimes make the cancer less responsive to later treatment. ¹

Surgery

Surgery is not usually the main treatment for lymphoma because the cancer often affects multiple parts of the body. However, surgery may sometimes be useful when lymphoma creates a single mass, especially if it causes:

An intestinal blockage
A tear in the intestine
Severe bleeding
Another emergency problem

The veterinarian will decide whether surgery is appropriate based on the location and behavior of the cancer.

Radiation Therapy

Radiation therapy is not usually the main treatment for widespread multicentric lymphoma, but may be useful when lymphoma is concentrated in one particular area. It may be considered for certain:

Nasal lymphomas
Brain or spinal tumors
Skin tumors
Localized masses

Supportive and Palliative care

Not every family chooses chemotherapy. Some owners may decide that their main goal is keeping their pet comfortable rather than pursuing aggressive cancer treatment. This is a completely reasonable discussion to have with your veterinarian.

Supportive care may include:

Anti-nausea medications
Appetite stimulants
Pain medication
Fluids
Nutritional support
Steroids
Comfortable bedding
Help moving around
Stress reduction

fort and the pets’ quality of life rather than trying to eliminate the cancer. ¹

Palliative care focuses on com

Quality of life

When treating lymphoma, quality of life is just as important as survival time. The goal is not simply to keep a pet alive for as long as possible, but rather to help them have more good days. Many pets receiving chemotherapy continue to eat well, play, and enjoy their normal routines.

To estimate your pet’s quality of life, you can keep track of several basic things:

Does your pet seem comfortable?
Are they eating normally?
Can they keep themselves clean?
Do they still seem interested in the things they normally enjoy?
Can they stand, walk, and move around comfortably?
Are there still more good days than difficult days?

Writing down your pet’s good and bad days can make it easier to notice gradual changes.

Lymphoma in cats and dogs:
key takeaways

Lymphoma is a serious cancer, but a diagnosis does not mean that your pet has no options. The disease can look very different from one animal to another. Some pets develop large lymph nodes, while others simply lose weight or develop digestive problems.

The most important steps are to: recognize changes early, see your veterinarian promptly, get a proper diagnosis, find out what type of lymphoma your pet has, discuss treatment and quality of life.

Statistics can help veterinarians understand what usually happens, but they cannot predict exactly what will happen to your individual dog or cat.

For many families, the goal of lymphoma treatment is not simply to add more time. It is to make that time comfortable, happy, and full of the things your pet loves.

Lymphoma in Cats and Dogs: Frequently Asked Questions

Is lymphoma contagious?

No. Lymphoma is a cancer and cannot be spread from one pet to another through normal contact. However, some viruses associated with lymphoma, such as FeLV, can spread between cats. This is one reason testing and prevention are important. ⁴

Can my dog or cat be cured?

Usually, lymphoma is considered treatable rather than curable. Some pets can have very long remissions, but the cancer may eventually return. The main goal of treatment is usually to achieve remission. ¹ ²

How long a pet stays in remission depends on many things, including:

The type of lymphoma
Whether it is B-cell or T-cell
Where the lymphoma is located
How advanced the disease is
How sick the pet is when treatment begins
How well the cancer responds to treatment

Because of these differences, two pets with lymphoma can have very different outcomes.

Does chemotherapy make pets feel sick?

It can, but most pets tolerate chemotherapy better than people often expect. Possible side effects include:

Vomiting
Diarrhea
Reduced appetite
Tiredness

Most side effects are manageable, and veterinary chemotherapy is designed to protect quality of life. ¹

Can lymphoma come back after treatment?

Yes. This is called relapse. A pet can be in remission and later develop lymphoma again. If this happens, the veterinarian may discuss another chemotherapy protocol or other treatment options. ¹

Is lymphoma painful?

Lymphoma itself is not always painful. For example, the enlarged lymph nodes seen with multicentric lymphoma are often painless. However, lymphoma can become painful if it affects certain organs, causes pressure, blocks an organ, or leads to other complications. Good pain control and supportive care can help keep affected pets comfortable.

Is Lymphoma Common?

Yes. Lymphoma is one of the most common cancers diagnosed in both dogs and cats.

In dogs, lymphoma is the most common blood-cell cancer and makes up a large proportion of cancers involving the lymphatic and blood-forming tissues. ¹ ²

In cats, lymphoma is also one of the most common cancers diagnosed by veterinarians. ³ ⁴

Can Lymphoma Be Prevented?

There is no guaranteed way to prevent lymphoma. However, good general healthcare can help reduce some known risks and may help detect disease earlier.

For cats, important steps include:

Testing for FeLV and FIV when recommended by your veterinarian
Discussing FeLV vaccination with your veterinarian
Reducing exposure to cats that may carry infectious diseases
Taking unexplained weight loss or changes in appetite seriously
Having regular veterinary checkups

For dogs, regular veterinary examinations can help detect enlarged lymph nodes or other unusual changes early. Most importantly, remember that having a risk factor does not mean your pet will develop lymphoma, and avoiding every possible risk factor cannot guarantee that lymphoma will not develop.

Moses Chang

Veterinary student & content contributor

Doctor of Veterinary Medicine Candidate, University of Sydney

Moses Hyunmin Chang is a 4th year Doctor of Veterinary Medicine student at the University of Sydney with a background in animal sciences from UC Davis. With clinical experience spanning small animal, equine, livestock, and wildlife medicine across both the US and Australia, he brings a broad, cross species perspective to veterinary care.

Clinical rotations spanning small animal, equine, livestock, and wildlife medicine
Emergency and critical care experience at Veterinary Emergency Group, California
Bachelor of Science in Animal Sciences, University of California, Davis

LEARN MORE ABOUT MOSES

Merck Veterinary Manual. Malignant Lymphoma in Dogs. Merck Veterinary Manual. Updated September 2024. https://www.merckvetmanual.com/dog-owners/blood-disorders-of-dogs/malignant-lymphoma-in-dogs[↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩]

Merck Veterinary Manual. Lymphoma in Dogs. Merck Veterinary Manual. Updated April 2025. https://www.merckvetmanual.com/circulatory-system/lymphoma-in-dogs/lymphoma-in-dogs[↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩]

PetMD. Lymphoma in Cats. PetMD. https://www.petmd.com/cat/conditions/cancer/c_ct_lymphoma[↩][↩]

Merck Veterinary Manual. Feline Leukemia Virus Disease. Merck Veterinary Manual. https://www.merckvetmanual.com/infectious-diseases/feline-leukemia-virus/feline-leukemia-virus-disease[↩][↩][↩]

Bennett PF, Taylor R, Williamson P. Demographic risk factors for lymphoma in Australian dogs: 6201 cases. Journal of Veterinary Internal Medicine. 2018;32(6):2054–2060. https://academic.oup.com/jvim/article/32/6/2054/8471016[↩]

Bertone ER, Snyder LA, Moore AS. Environmental and lifestyle risk factors for canine lymphoma. Veterinary and Comparative Oncology. https://doi.org/10.1111/j.1939-1676.2003.tb02478.x[↩]

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Lymphoma in Dogs and Cats: Everything you need to know

What is Lymphoma?

High-grade vs. low-grade Lymphoma

Dogs and cats get different types of Lymphoma

What causes Lymphoma and which pets are at risk?

What are the signs and symptoms of Lymphoma in pets?

How is Lymphoma diagnosed?

Staging Lymphoma

How is Lymphoma treated?

Quality of life

Lymphoma in cats and dogs: key takeaways

Lymphoma in Cats and Dogs: Frequently Asked Questions

Moses Chang

References

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Lymphoma in cats and dogs:
key takeaways