Lymphoma in Dogs: Symptoms, Stages, and Treatment

Lymphoma in dogs is a common type of cancer that begins in the lymph nodes and spreads throughout other parts of the body.  

Affected dogs experience concerning symptoms, such as weight loss, enlarged lymph nodes, and poor appetites.  

Lymphoma cancer in dogs is not curable, but with prompt diagnosis a veterinarian can provide an appropriate treatment plan for the best outcome.  

What Is Lymphoma in Dogs?

Lymphoma, also known as lymphosarcoma (LSA), is one of the most common cancers in dogs.  

Lymphoma in dogs occurs when there’s an overgrowth and unregulated cellular division of lymphocytes, a type of cell that plays a crucial role in the immune system that helps protect the body from infection. 

Although lymphoma in dogs can affect any organ of a pup’s body, it primarily affects parts of the immune system, including the lymphatic system, lymph nodes, spleen, and bone marrow.  

The lymphatic system is interconnected with the bloodstream, which is why lymphoma in dogs is considered a systemic (whole body) disease and, as such, requires treatment such as chemotherapy. 

Types of Lymphoma in Dogs

There are several types of lymphoma in dogs, categorized by the organs affected. The most common are: 

• Multicentric lymphoma. This type is first noted in the lymph nodes. 

• Gastrointestinal lymphoma. This affects the stomach and intestines. 

• Cutaneous lymphoma. This type of lymphoma of affects a dog’s skin. 

Less common types of lymphoma in dogs include: 

• Extranodal lymphoma. This is an uncommon form that occurs when lymphoma develops in an organ outside the lymphatic system, such as an eye or kidney. 

• Mediastinal lymphoma. This type is also uncommon. This occurs when lymphoma affects the lymphoid organs within the chest cavity that support the immune system. 

Symptoms of Lymphoma in Dogs

The most common symptom of lymphoma in dogs is an enlarged, firm, non-painful lymph node.  

Dogs have multiple pairs of lymph nodes throughout the body, but the easiest lymph nodes to locate and feel are the prescapular (front of chest), submandibular (under the jaw), and popliteal (behind the knees).  

Usually one, both, or multiple nodes are enlarged. 

Other symptoms of lymphoma in dogs include:  

• Weight loss 

• Decreased appetite 

• Swelling of the face or limbs 

• Increased thirst and urination 

Symptoms of lymphoma in dogs that are specific to the body area affected can also include:  

• Dry, crusty skin with patches of hair loss, loss of color, and ulcerated skin 

• Diarrhea and vomiting 

• Exercise intolerance 

• Coughing 

• Difficulty breathing  

Stages of Lymphoma in Dogs 

Lymphoma in dogs can be classified into five stages depending on the number of body systems affected: 

• Stage I: At this stage, a single lymph node affected. This is the earliest form of the disease and the most treatable. Some dogs may not have any other symptoms besides one swollen lymph node, while others may start experiencing lethargy and weight loss.  

• Stage II: At this stage, multiple lymph nodes affected in a similar region. Cancer is limited to one area of the body, so it is generally treatable with chemotherapy. Dogs often have poor appetites, lethargy, and some weight loss during this stage. 

• Stage III: All lymph nodes affected at this stage. Once widespread, chemotherapy is necessary for treatment. Symptoms vary during this stage, but the prognosis is less favorable compared to earlier stages.   

• Stage IV: All lymph nodes and some organs (spleen, liver, chest) are affected. This is a severe stage of widespread disease with a poor prognosis, but chemotherapy can extend the life expectancy if begun promptly. Dogs generally need supportive care to manage their symptoms, such as vomiting, increased thirst, and weight loss.  

• Stage V: At this stage, there’s bone marrow involvement. This is the most serious stage of disease with the poorest prognosis. Dogs appear very ill and require an aggressive approach to chemotherapy. 

Causes of Lymphoma in Dogs

Lymphoma in dogs often occurs for reasons that are not well understood. Multiple factors that have been associated with certain cancers include: 

• Age 

• UV damage or other environmental triggers, such as exposure to cigarette smoke 

• Certain viruses and infections, such as ehrlichiosis 

• DNA mutations that affect some breeds, such as Boxers and Golden Retrievers  

• Genetics 

There’s rarely a single cause for cancer, and the development of lymphoma is no different. 

How Veterinarians Diagnose Lymphoma in Dogs

In most cases, the first sign of lymphoma in dogs is enlarged lymph nodes.  

From there, your veterinarian may want to perform a cytology (when a needle is inserted into the node and cells are obtained) or biopsy of the lymph node and have the sample reviewed by a pathologist. 

Once your dog is diagnosed, your veterinarian may recommend additional tests, such as:  

• Chest X-rays 

• Abdominal ultrasound 

• Blood work 

• Bone marrow aspirates  

• Immunohistochemistry, which identifies the type and stage of cancer present using special stains in a laboratory 

• Flow cytometry, which separates cancerous cells from healthy cells so a veterinarian can choose the most appropriate treatment 

Your vet may refer you to an oncologist for further testing and treatment—including staging—to determine how far the cancer has spread.  

Treatment of Lymphoma in Dogs

Lymphoma in dogs is one of the cancers that is most responsive to chemotherapy, and remission can often be achieved in well over 50% of dogs.  

Dogs tolerate chemotherapy much better than people do, and the doses prescribed are often lower, with fewer side effects than expected because the goal of treatment is to preserve the quality of your dog’s life for as long as possible.  

Some side effects can occur, such as: 

• Decreased appetite 

• Lethargy 

• Mild vomiting and diarrhea 

Serious side effects, such as bone marrow suppression and secondary infections, can occur, but are not as common. Most dogs do not lose their hair, but wire-haired breeds, such as Poodles, often do lose their hair. 

An oncologist can help decide the best medication or medications for your dog.  

There are multiple chemotherapeutic medications used in the treatment of lymphoma in dogs, including: 

• Lomustine 

• Vincristine 

• Prednisone 

• Cyclophosphamide 

• Chlorambucil 

• L-Asparaginase 

In some cases, your vet may recommend removal of a lymph node or organ affected by lymphoma. 

If chemotherapy is not an option, speak with your vet about the use of steroids alone.  

Although not a first line of treatment, prednisone can improve clinical signs and increase the comfort of your pet, if only for a few weeks. 

Despite the most aggressive of treatments, lymphoma in dogs can’t be cured, and most dogs will relapse at some point. 

A second remission, though more difficult, can be achieved for some dogs.  

Humane euthanasia may be recommended when the cancer and its effects can no longer be controlled. 

Recovery and Management of Lymphoma in Dogs

Although lymphoma in dogs can be treated and many dogs go into remission, it can’t be entirely cured.  

You can expect the cancer to return, and another round of chemotherapy—often a different protocol than previously given—will be needed to achieve remission, which can be quite difficult.  

The vet should continue to examine your dog frequently for signs of relapse (often seen with enlarged lymph nodes), and it’s important to follow recommendations for recheck exams and follow-up testing. 

Additionally, remember that quality of life instead of quantity is the goal for your dog with lymphoma.  

The side effects and treatments are often not as severe as what is seen in human medicine, and dogs can maintain a normal, happy and positive life throughout treatment and follow-ups. 

At home, you can provide your dog a comfy bed to rest in.  

Providing ramps or dog stairs to help them with their mobility is also useful.  

Prevention of Lymphoma in Dogs

While it can be difficult to prevent many cases of lymphoma, pet parents can take steps to reduce their pet’s risk, which may include:  

• Refrain from smoking in the house and around your pet. 

• Support a healthy diet and appropriate weight in your dog. 

• Prioritize regular veterinary wellness care to identify issues early.  

• Reduce your dog’s exposure to toxins and chemicals in the house or yard.