Lymphoma in Cats and Dogs

What is lymphoma?

Lymphoma is a type of cancer that arises from lymphocytes, which are white blood cells that play a key role in the immune system. These cells are normally found in tissues such as the lymph nodes, spleen, bone marrow and other organs. In pets the term “lymphoma” refers to a group of related diseases rather than a single illness.

In dogs, lymphoma is one of the most common cancers of the blood and lymphatic system.
In cats, lymphoma also occurs relatively often and can appear in many parts of the body such as the gastrointestinal tract, chest or other areas.

As it can affect different organs, the way lymphoma behaves and responds to treatment can vary significantly. Early consultation with your veterinary surgeon is strongly advised.

Signs and symptoms, what might you notice?

The signs of lymphoma depend on which organs are affected.

In dogs:
Enlarged lymph nodes are often the first noticeable change, especially those under the jaw, in front of the shoulder or behind the knee. Some dogs may show loss of appetite, weight loss, lethargy, vomiting or diarrhoea if the digestive tract is involved. In certain cases, increased drinking or urination may occur due to high blood calcium levels.

In cats:
Gastrointestinal lymphoma is the most common type. Signs may include chronic vomiting, diarrhoea, weight loss or changes in appetite. Cats with lymphoma in the chest may have breathing difficulties or a cough. Occasionally there may be a noticeable mass or swelling in the abdomen.

Since these signs can be non-specific, it is important not to assume they are simply due to ‘getting older’. Any persistent or unexplained change should always be checked by your vet.

Diagnosis and staging

If your vet suspects lymphoma, they may recommend tests to confirm the diagnosis and determine how far the disease has progressed. This is known as staging, and helps inform the treatment plan. Diagnostics may include a fine needle aspirate or biopsy of a lymph node or mass, blood tests, and sometimes special tests to determine whether the cancer involves B-cells or T-cells. The subtype can influence both treatment choice and prognosis.

Imaging such as ultrasound or X-rays may be used to evaluate internal organs and lymph nodes. In cats, especially those with suspected intestinal involvement, abdominal imaging and intestinal biopsies are common. Staging results help the veterinary team plan the most appropriate treatment and discuss realistic outcomes with you.

Treatment options

Treatment aims to achieve remission, where signs of disease are minimal or absent, while maintaining good quality of life.

In dogs, multi-drug chemotherapy protocols remain the standard of care. Many dogs go into complete remission and enjoy months of good quality life. The average remission period is around seven to ten months, with median survival typically between ten and fourteen months for many treated dogs. Prognosis depends on factors such as lymphoma subtype, stage, and individual response to therapy. Advances in veterinary oncology, including genetic profiling, are helping refine treatment options and improve long-term outcomes.

In cats, chemotherapy is also the main form of treatment. Many cats achieve remission rates between 65 and 75% in moderate to high-grade disease. Cats with low-grade or small-cell lymphoma, particularly in the intestines, may respond well to less intensive oral chemotherapy and can live comfortably for extended periods. Radiation therapy may also be used in select cases, such as lymphoma in the nasal cavity or other localised areas, although it is less common than chemotherapy.

What it means for you and your pet

Facing a cancer diagnosis in your pet is emotionally challenging. The most important point to remember is that quality of life always comes first. The aim of treatment is not simply to extend your pet’s life but to ensure that their life remains happy, comfortable and worth living. Your vet will explain potential side effects, how treatment is monitored and what outcomes you can expect. Chemotherapy or specialised treatments can be expensive and often involve regular visits, so it helps to discuss costs and logistics early on to make sure the plan feels realistic for your household.

Ongoing communication with your veterinary team is essential. Regular check-ups allow your vet to monitor your pet’s response to therapy and adjust treatment as needed. Some owners choose supportive care rather than aggressive therapy, while others pursue full treatment protocols. There is no single correct choice. What matters most is what feels right for you, your family and your pet. It is also important to look after yourself, caring for a pet with cancer can be emotionally draining. Reaching out for help from veterinary support staff, friends or pet-counselling services can make a real difference.

What you can do to help your pet

Keep a close eye on your pet’s general condition, including appetite, weight, energy levels, drinking and urination habits, bowel movements and any new lumps or swollen lymph nodes. Ask your vet which specific signs you should watch for and report promptly. Ensure that recommended tests or follow-up visits are attended, since early or ongoing treatment often leads to better results.

At home, focus on keeping your pet comfortable. Offer good nutrition, a quiet resting place and attentive care if any treatment side effects occur such as nausea or digestive upset. Follow your vet’s guidance closely regarding medication and monitoring. Discuss realistic treatment goals from the beginning so that you understand what remission might look like, what timeframe to expect and when it may be appropriate to shift focus from active treatment to supportive or palliative care. Above all, continue giving your pet the affection and reassurance that mean so much to them throughout this journey.

Summary

Lymphoma is a serious disease in both dogs and cats, but outcomes vary greatly depending on species, subtype, stage and the treatment chosen. With early diagnosis and appropriate care, many pets can enjoy several months to more than a year of good quality life. Cats with low-grade lymphoma may live comfortably for even longer.

The best thing you can do is work closely with your veterinary surgeon, communicate openly, and make decisions that align with your goals and your pet’s comfort. If you notice persistent swelling, weight loss, appetite changes, vomiting, diarrhoea or any ongoing decline, contact your vet promptly. Early action gives your pet the best chance effective treatment.