Lymphoma in dogs: Symptoms, stages, and treatment options

Receiving a diagnosis, or having a suspicion, that your dog has lymphoma is a very distressing situation to be in for any owner. Most people are well aware of the seriousness of a cancer diagnosis, that the disease can take hold quickly and that treatment options can be sadly limited. Lymphoma is not a single disease but covers a specific group of cancers. While it is a very serious condition, it is one of the most treatable groups of cancers.

What is lymphoma in dogs?

Lymphoma refers to cancer affecting the lymphocytes (a type of white blood cell, part of the immune system) and the lymphatic system in the body. It can occur anywhere in the body, as these cells are present throughout the body and bloodstream. It is classified into different types and stages, and can be isolated to one location, or spread throughout the body, with organs that contain large numbers of these cells, such as the lymph nodes, spleen and bone marrow being common sites. It accounts for 15-20% of new cancer diagnosis in dogs.

Why do dogs get lymphoma? (causes and risk factors)

Lymphoma can occur in dogs of any age, but is most common in middle aged dogs, aging from ~ 6-9 years old. Like many cancers, an exact cause is often unknown. Genetics and some environmental factors (such as exposure to certain types of herbicides (2,4-D specifically)) may play a role in some cases, with certain breeds known to be at a higher risk of developing lymphoma. There seems to be some variations in specific breeds at higher risk depending on country. Breeds that may be at higher risk for developing lymphoma include Golden Retrievers, Labradors, German Shepherds, Boxers, Bernese mountain dogs, Beagles, Dobermans, English cocker spaniels, Bulldogs, and Rottweilers.

Recognising Lymphoma Symptoms in Dogs

Common Signs to Watch For:

Swelling of lymph nodes (usually painless) is often the first identifiable sign – The easiest lymph nodes to feel when enlarged include.
- Under the jaw/upper neck (Submandibular lymph nodes)
- Front of the shoulder (Pre-scapular lymph nodes)
- Armpits (Axillary lymph nodes)
- Inner thigh/groin area (Inguinal lymph nodes)
- Behind the knees (Popliteal lymph nodes).
Lethargy and weight loss
Increased thirst and urination.
Specific Symptoms: Sometimes clinical signs will be more specific depending on which area is affected by the lymphoma. Examples of this include.
- Mediastinal lymphoma or lymphoma that has spread to the lungs, causes difficulty breathing (E.g. shortness of breath, laboured breathing, exercise intolerance, coughing).
- Alimentary lymphoma causes gastrointestinal signs like vomiting, diarrhoea, abdominal distention, and weight loss.
- When lymphoma spreads to areas and organs outside the lymphatic system, such as the skin, eyes, and kidneys, it is referred to as extra nodal lymphoma. This is the rarest lymphoma type. This can cause various signs dependant on the location, from red patches, hair loss, or ulcers of the skin, eye discharge, sudden blindness, bleeding or masses seen on/in the eye or eyelids.

The 5 Main Types of Canine Lymphoma

Multicentric Lymphoma:

This is the most common form of lymphoma in dogs (~80-85% of lymphoma cases) and occurs when cancer cells infiltrate lymphoid tissue (lymph nodes and the lymphatic system). Internal organs such as the liver, spleen, and bone marrow, are commonly involved with this type also. Depending on the stage of disease some dogs will be clinically well or only have mild, vague signs such as lethargy and decreased appetite, with enlarged lymph nodes palpable. Others will have more severe symptoms such as weakness, breathing issues, weight loss, vomiting and diarrhoea.

Alimentary (Gastrointestinal) Lymphoma:

This type of lymphoma infiltrates the stomach, intestines and surrounding internal lymph nodes. It can also include other organs. The lining of the intestine/stomach may have distinct masses present or significant thickening of the gut lining by cancer cells and surrounding inflammation. This presentation usually results in clinical signs such as weight loss, vomiting, diarrhoea, lethargy and poor appetite.

Cutaneous (Skin) Lymphoma:

Lymphoma affecting the skin (epitheliotropic lymphoma) can affect anywhere on the skin and include sites such as the footpads, oral cavity, with external lymph nodes and internal organs affected depending on the stage of disease. These skin lesions most commonly appear as scaly, red, or itchy skin (can be very itchy in some cases). There may be bumps present within or below the skin, ulcerations and secondary infections are common.

Mediastinal Lymphoma:

The mediastinum is a cluster of lymph tissue found in the lower chest of dogs, siting in a small space in front of the heart and between the lungs and the chest wall. When lymphoma develops here it causes a mass to grow in this spot, which puts pressure on the lungs, trachea, oesophagus and heart, worsening with the size of the mass. This type of lymphoma can occur on its own or be involved with multicentric lymphoma. This can present with vague signs early on, such as lethargy, vomiting/regurgitation, weight loss and poor appetite but inevitably leads to difficulty breathing as the mass grows. Clinical signs such as laboured breathing, higher respiratory rates, difficulty exercising, coughing and weakness are common.

Bone Marrow Lymphoma (Leukaemia):

Cancer that is isolated to the bone marrow and blood stream is categorised as leukaemia. Lymphocytic leukaemia can be further categorised into acute or chronic types (Significantly different prognosis for each) and graded based on the type of lymphocyte cells (B or T cell) that are most prevalent, which further helps vets determine what treatment is needed, how aggressive the disease is and the likely prognosis. With lymphocytic leukaemia there is an overabundance of cancerous lymphocytes produced, and these take up the space and production potential for other red and white blood cells in the bone marrow. Low white blood cells result in a significantly decreased immune system which makes the body much more susceptible to infections, and they will have poorer wound healing. Red blood cells carry oxygen around the body, so when they are low (anaemia) dogs will tire easily, be lethargic and often have changes to their breathing, having to try to compensate for these low oxygen levels by breathing faster or having more laboured/efforted breaths. If platelets (The cells responsible for blood clotting) are also affected, then dogs can have bleeding issues.

Determining the Severity: Lymphoma Stages in Dogs

Once a diagnosis of lymphoma is made your vet will recommend further testing to determine the stage of lymphoma. This is important to determine the prognosis for the disease and what treatment options are available and most appropriate for your dog. The stages of lymphoma increase with aggression and spread of disease and are staged from I to V, with a sub-stage added. Sub staging is included to help with assessment of prognosis and is categorised as either A (Feeling well) vs B (Feeling sick). The five stages of lymphoma are listed below:

Stage I: Single lymph node involved or lymphoid tissue in a single organ.
Stage II: Multiple lymph nodes involved but in a regional area (E.g. Just the lymph nodes on the front or back areas of the body).
Stage III: All or multiple external lymph nodes involved *This is the most common stage of diagnosis
Stage IV: Stage I, II or III with liver and/or spleen involvement.
Stage V: Stage I, II, III or IV with spread within the blood, and involvement of bone marrow, central nervous system or other organ systems.

Diagnosis and Testing at Greencross Vets

To diagnose lymphoma, then determine the stage and type, your vet will perform a thorough step by step diagnostic approach. The below list is a set of steps your vet will likely recommend, though the results of each step along the way may alter the order or specific tests they recommend. This will allow the most thorough assessment and the best treatment recommendation for your dog.

Physical Exam: This is a very important first step. A thorough physical exam allows the vet to check all external lymph nodes, palpate their abdomen, listen to their heart and lungs, and assess the rest of their body for any signs of lymphoma or other disease. This step alone already helps start the staging process and determine which test/s are most important to perform next and what treatment your dog needs right now for support.
Fine Needle Aspirate (FNA): This can often be performed conscious, but if the enlarged lymph node is in a difficult to reach location, or they are too stressed to allow this, then sedation may be required. A simple needle and syringe are used to draw cells from within enlarged lymph nodes. These are then placed on a slide for microscopic examination to check for cancerous lymphocytes and any other abnormal changes.
Staging Tests: This includes blood tests, and imaging such as X-rays and Ultrasound. These tests are extremely important to determine if/where the disease has spread and determine the stage and prognosis of the disease.
Immunophenotyping: Special stains/dyes can be applied to the cell samples submitted to diagnose lymphoma. This can determine if the lymphoma is B-cell, T-cell or mixed. This is critical for prognosis and treatment, as T-cell and B-cell lymphoma in will often act differently to each other, with T-cell generally considered to be more aggressive and having a poorer prognosis than B-cell lymphoma.

Treatment Options: Can a Dog Recover from Lymphoma?

The treatment options and outcomes for dogs suffering from lymphoma are variable and depend on factors such as the primary site, stage and type of lymphoma, other clinic disease present and how quickly treatment is started. The most common management/treatment options for lymphoma are discussed below.

Chemotherapy: In the vast majority of lymphoma cases chemotherapy is the recommended treatment, as cancerous lymphoma cells are typically quite sensitive to chemotherapy treatments. Multi-drug protocols generally result in the longest remission times, so are the most highly recommended treatment plans. Single drug therapy can still be very effective, however the time remission is maintained is often less, so long term outcome is not as favourable with this protocol. Cancer cells develop resistance to chemotherapy drugs over time, so by using a combination, remission times tends to be longer. Most dogs tolerate chemotherapy better than humans and generally stay well in themselves, with minimal side effects. They rarely experience hair loss or become significantly unwell with treatment. The most common side effects seen during treatment include vomiting, diarrhoea and decreased appetite. In veterinary medicine quality of life is a very important consideration in all our treatment choices, with the goal of chemotherapy in dogs to extend good quality life, without causing toxicity with the drugs used or significant side effects.
Palliative Care (Prednisolone): If chemotherapy is not an option, then palliative care using corticosteroids (Prednisolone) is usually recommended. This medication can yield temporary remission and provide other helpful effects including reducing inflammation in the body and increasing appetite. In most cases this medication will improve quality of life significantly and dogs will feel a lot better. Unfortunately, the effects are temporary and eventually the cancer resurges and the drug will lose its efficacy. Remission, if achieved with this medication, generally lasts a much shorter time than with chemotherapy, but will make them much more comfortable in the short term.
Diet & Nutritional Support: Diet modification and nutritional support can be helpful for quality of life in dogs battling cancer. It is important to note that there is no proven diet or supplement that actively kills cancer cells. Cancer fights the body for nutrition, and it is very common for dogs to lose weight and muscle condition rapidly. The purpose of a cancer-support diet is to help maintain your dog’s muscle condition, body weight, and appetite, improving their quality of life during this time. The main dietary techniques utilised can include low carb, high quality protein, moderate fat diets with high levels of Omega 3s. Adding in some additional foods to the diet such as lean meats, eggs, cottage cheese and some specific vegetables and fruits are sometimes suggested to help stimulate appetite and add in some additional nutritional support. The basic principles behind this type of diet are that cancer cells tend to use anaerobic metabolism and so use carbohydrates, more than fats, for energy. By depriving them of this energy source, we can potentially slow their progress and provide dogs with alternative energy sources their body can use more easily.
There are some prescription diets that are made to support dogs with cancer, such as Hills Onc Care. There is sometimes talk of feeding raw food, to be nutritious and add proteins, however dogs fighting cancer and undergoing chemotherapy often have compromised immune systems, so feeding raw food increases their risk of infection, so is not usually recommended. Omegas 3s, particularly EPA and DHA, have been proven to have some anti-cancer properties, plus they have natural anti-inflammatory action also. This combination makes them an ideal supplement to help support dogs with cancer.

Prognosis: What to Expect

80-90% of dogs with multicentric lymphoma will achieve remission with chemotherapy, however “remission” does not mean “cure” and sadly most lymphoma patients will have recurrence of the lymphoma at some stage. Remission can be defined as a resolution of detectable cancer and related symptoms. Remission achieved through chemotherapy will on average provide dogs much longer survival times, expected to be 8-12months (~12months for B-cell and ~6-8months with T-cell). Without any treatment or palliative care (prednisolone) the average life expectancy is ~4-6 weeks after diagnosis. Prednisolone can yield temporary remission with ~1-2months survival times on average, whereas with no treatment it is common for dogs to pass in less than 4weeks on average. Remission rates for other forms of the disease, including the gastrointestinal and cutaneous forms, are not as high.

When to See a Vet

Swollen/enlarged lymph nodes are commonly found as the first visible sign of lymphoma, before your dog becomes unwell, so regular checks at home of the previously mentioned lymph node sites and a vet visit ASAP upon noticing any change is very important. Given the vague signs lymphoma can start with, any other signs of concern such as persistent lethargy, changes to breathing pattern or exercise intolerance warrants a vet check urgently also. Early intervention will result in the best chance at treatment for this disease.

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This article was written by Dr. Jade Ridsdale, BSc BVMS

Dr Jade is a Greencross Vets WebVet with over 13 years experience as a veterinarian in multiple small animal practices around Western Australia.