Lymphoma in cats – symptoms, diagnosis and treatment

When to see a vet urgently

When lymphoma is suspected, the urgency of care depends on the symptoms. An emergency assessment is needed immediately if:

your cat has laboured breathing or breathes with their mouth open;
your cat collapses or becomes unusually unresponsive;
repeated vomiting is accompanied by severe abdominal pain and weakness;
your cat is very subdued, does not eat and deteriorates rapidly.

Do not wait for biopsy results when symptoms are serious: find a vet near you.

Overview

Lymphoma is a systemic cancer in which malignant lymphocytes spread to different parts of the body. Intestinal and mediastinal lymphoma are among the most common forms in cats, while skin and kidney lymphoma are less common. The disease can progress rapidly and cause a dramatic deterioration or follow a chronic course. It occurs in cats of all ages, but most often in adult and older cats.

Lymphoma is not a single disease that always progresses in the same way. Small-cell, low-grade intestinal lymphoma often progresses more slowly than the large-cell, high-grade form. Location and cell type affect investigations, treatment and prognosis. Intestinal lymphoma is now common in cats, and enlarged external lymph nodes are not a feature of every case.

Although lymphoma is generally considered a systemic disease affecting the whole body, some forms can be localised. Treatment for lymphoma in the nasal cavity, for example, may therefore differ from treatment for widespread disease. Its extent is investigated individually: the word lymphoma alone does not identify every affected organ.

Causes

The exact causes of lymphoma are not fully understood, but predisposing factors include:

Feline leukaemia virus, or FeLV, one of the most important risk factors.
Feline immunodeficiency virus, or FIV, which reduces the immune system's ability to keep tumour cells in check.
An inherited predisposition.
Chronic inflammation, such as inflammatory bowel disease.
Exposure to carcinogens and toxic substances.

The association with viruses varies between forms of the disease. FeLV is clearly linked to certain high-grade forms, but many cats with low-grade intestinal lymphoma test negative for FeLV and FIV. Conversely, a positive viral test does not diagnose lymphoma. The presence of a tumour and a viral infection are investigated as separate questions.

A possible link between chronic intestinal inflammation and small-cell lymphoma is being studied. Inflammatory and cancerous changes can occur together, but not every case of inflammatory bowel disease inevitably becomes cancer. Distinguishing them can be difficult even in a tissue sample, so diagnosis sometimes requires a combination of methods.

Risk factors

Cats that test positive for FeLV or FIV.
Young cats, more often with a virus-associated form, and older cats with sporadic cases.
Cats in homes where people smoke, as passive smoking increases lymphoma risk, and cats from poorly managed breeding establishments.
Crowded conditions and stress.

An association between tobacco smoke exposure and lymphoma has been found in an observational study. This alone does not show that smoke caused a particular cat's tumour. Cat-specific evidence on the independent lymphoma risk associated with crowding, stress or descriptions of a breeding establishment's quality is limited. A list of risk factors therefore does not replace diagnosis or explain why an individual cat became ill.

Typical symptoms

Symptoms depend on where the tumour is located:

Intestinal lymphoma: chronic diarrhoea, vomiting, weight loss and abdominal swelling.
Mediastinal lymphoma: shortness of breath, coughing and difficulty breathing because fluid accumulates in the chest.
Kidney lymphoma: enlarged kidneys and signs of kidney failure.
Skin lymphoma: lumps, thickened areas and skin ulcers.
General signs: listlessness, reduced appetite and progressive weight loss.

With intestinal lymphoma, appetite may be reduced, normal or increased despite weight loss. Clinical examination and routine blood tests may reveal few abnormalities. Similar digestive symptoms can occur with other intestinal diseases, so persistent diarrhoea or vomiting cannot be labelled lymphoma on the symptoms alone.

Fluid in the chest makes it harder for the lungs to expand and can cause breathing difficulty. In this situation, supporting breathing may take priority over extensive cancer investigations. With kidney lymphoma, thirst, vomiting and loss of appetite may be more prominent. The tumour's location affects what you first notice at home.

Complications and consequences

Untreated lymphoma leads to:

a severe deterioration in general health;
damage to multiple organs;
internal bleeding;
fluid accumulation in the chest or abdomen;
death.

Complications and the speed at which they develop vary with the form of the disease. Slowly progressing intestinal lymphoma is assessed differently from a rapidly growing lymphoma causing severe organ dysfunction. Not every cat develops all the consequences listed. Treatment goals are matched to the diagnosed disease and the cat's general condition.

Diagnosis at the vet

Diagnosis uses:

examination of lymph nodes and organs by touch;
ultrasound of the abdomen and chest;
chest X-rays;
cell or tissue samples from a lymph node or tumour;
blood tests to assess other changes;
FeLV and FIV tests.

Cytology examines collected cells, whereas a tissue sample also shows tissue structure. A fine-needle sample may be enough for some lymphomas, but distinguishing small-cell intestinal lymphoma from inflammation may require a biopsy. Samples can be taken by endoscopy or surgery. The method depends on the location of the changes and the sample needed.

A tissue examination may be supplemented with stains that reveal cell characteristics or a PARR test, which looks for evidence of expansion of a cell population derived from one original cell. However, PARR is not a conclusive cancer test on its own. Results are interpreted alongside clinical findings and tissue examination. Thickening of the intestine on ultrasound also cannot, on its own, distinguish inflammation from lymphoma.

Stage and grade provide different information. Staging investigates where the disease is present and whether it affects organ function. Grade is assessed from the characteristics of the cells and tissue. The vet explains what an additional test would establish and how it would affect treatment choices. Not every possible test is needed for every cat.

Treatment and follow-up

Chemotherapy is the main treatment for most lymphomas. Low-grade intestinal lymphoma may be treated with oral medicines, while more aggressive forms often require a combination of injectable medicines. Medicines, doses and monitoring are prescribed individually. Another cat's treatment programme must not be used for your cat.

Radiotherapy can be used for localised lymphoma in some circumstances. Surgery may be needed to obtain a sample or treat a local problem in the intestine, for example, but it does not usually replace medical treatment for systemic disease. Treatment is chosen according to the location, extent of disease and the cat's condition.

The aim of treatment is good quality of life and control of the disease. Cats often tolerate chemotherapy well, but nausea, diarrhoea or reduced appetite can occur. Monitoring helps assess both effectiveness and adverse effects. Contact the vet if you cannot give a medicine, your cat vomits it up or their condition changes. Do not adjust doses yourself.

If symptom-relieving treatment is chosen, it is planned just as carefully. Pain, nausea, appetite and fluid needs are assessed even when treatment directed at the tumour is not given. Palliative care means active symptom management and support for daily life. Its goals are agreed with the vet treating your cat.

What to monitor at home

Record eating, changes in weight, vomiting, stools and your cat's interest in normal activities. Treatment success is not judged only by tumour size. Keep food, water and the litter tray within easy reach, and reduce handling that disturbs rest. If your cat can no longer groom, you can help gently.

Do not force feeding if it causes resistance or distress. Nausea, pain and problems absorbing nutrients need their own assessment. The vet can plan nutritional support suited to your cat's situation. An agreed plan for deterioration helps you recognise when prompt additional help is needed.

Prognosis

Remission means that signs of the disease reduce or disappear in response to treatment; it is not the same as a guaranteed permanent cure. The outlook varies greatly with cell type, location, stage, general condition and treatment response. A single life expectancy estimate therefore cannot apply to every cat with lymphoma. The duration of the response is also assessed at follow-up visits.

Prevention

Vaccination against feline leukaemia virus for cats at risk: the vet assesses the need according to your cat's lifestyle and local infection risk.
FeLV and FIV testing, particularly in breeding establishments and rescue centres.
Avoid uncontrolled contact with potentially infected cats.
Support immunity with a varied diet and good care.

FeLV vaccination reduces FeLV-associated risk but does not prevent every form of lymphoma. Viral testing and contact management are planned according to lifestyle. Good nutrition and care support general health, but cannot guarantee that cancer will not develop. Not all lymphomas can currently be prevented.

Important for cat owners

Lymphoma is one of the most serious cancers in cats and requires early diagnosis and comprehensive treatment. Prompt chemotherapy can bring some cats into remission and substantially extend their lives. Be particularly alert to persistent diarrhoea, rapid weight loss or breathing difficulty. Seeking help early from a vet or a vet experienced in cancer treatment substantially improves the outlook.

Prompt investigation can allow treatment before a major deterioration. However, it does not determine prognosis on its own: the disease's biological characteristics and response to the chosen treatment are crucial. The distinction between a slower and a more aggressive form is established so that you receive an assessment specific to your cat.

This article provides general information and does not replace veterinary care. If you notice signs of illness in your cat, contact a vet.

Frequently asked questions

Can a cat with a negative FeLV test have lymphoma?

Yes. Many cats with low-grade intestinal lymphoma, for example, test negative for FeLV and FIV. A viral test does not replace a cell or tissue sample to identify a tumour.

Does thickening of the intestine on ultrasound confirm lymphoma?

No. Similar changes can appear in inflammatory bowel disease, and sometimes ultrasound looks normal despite lymphoma. Diagnosis may require a biopsy and additional tests.

Does remission mean that a cat is completely cured?

Not necessarily. Symptoms and detectable disease may reduce or disappear during treatment, but the disease can return later. Check-ups and monitoring continue according to the agreed plan.

This article is for general information only and is not a guide to treatment. If you notice the first signs of illness, contact your vet.

Paw4care editorial team

Sources

Lymphoma, Cornell University College of Veterinary Medicine, accessed 2026-11-03.
Lymphoma in Cats, VCA Animal Hospitals, accessed 2026-11-03.
2026 AAHA Oncology Guidelines: Overview of Common Cancers, AAHA, accessed 2026-11-03.
ACVIM consensus statement guidelines on diagnosing and distinguishing low-grade neoplastic from inflammatory lymphocytic chronic enteropathies in cats, ACVIM / Journal of Veterinary Internal Medicine, accessed 2026-11-03.
Section 3: Tumour Diagnostics & Staging, American Animal Hospital Association, accessed 2026-11-03.
Environmental tobacco smoke and risk of malignant lymphoma in pet cats, American Journal of Epidemiology, accessed 2026-11-03.
Home Care for the Cancer Patient, Cornell University College of Veterinary Medicine, accessed 2026-11-03.
2023 AAFP/IAAHPC Feline Hospice and Palliative Care Guidelines, AAFP / IAAHPC, Journal of Feline Medicine and Surgery, accessed 2026-11-03.
Initial Triage and Resuscitation of Small Animal Emergency Patients, Merck Veterinary Manual, accessed 2026-11-03.

Lymphoma in cats: symptoms, diagnosis, treatment and prevention