Lymphoma In Cats

Updated September 13, 2022

Lymphoma is the most common tumour of cats. It also can be one of the more treatable cancers depending on the type involved.

Lymphoma is caused by the abnormal multiplication and growth of lymphocytes. These are a white blood cell found throughout the body, including the bloodstream, gut and lymph nodes.

Signs Of Lymphoma

The main signs of lymphoma in cats are vague illness, weight loss and reduced appetite. Other signs depend on the organ affected by the tumour, and can include:

  • Diarrhoea (see other causes at the link)
  • Abnormal swellings
  • Drinking more
  • Intermittent vomiting
  • A runny or blood nose

Diagnosis of Lymphoma

The diagnosis of lymphoma in cats is rarely straightforward. It often starts with seeing the vet for a vague general sign like weight loss. A physical exam might suggest blood testing, leading to further tests like an ultrasound exam.

Only a surgical biopsy will give an accurate diagnosis. A needle biopsy alone, while useful, can only tell you that it’s lymphoma. It’s essential to know what type of lymphoma it is before you make a decision on whether to treat or not.

Two other causes of abdominal lumps easily confused without investigation are FIP and hairballs.

High grade alimentary lymphoma and renal lymphoma have a very poor prognosis. Reported median survival times even with treatment are only around 3 to 4 months. That’s in contrast to nasal lymphoma and small cell alimentary lymphoma which have reported survival times of several years with treatment. There is even a solitary form which can be surgically cured, but this is rare.

Beware of older information giving a blanket statement like “cats live on average for a year after diagnosis of lymphoma.” This figure derives from studies where the types of lymphoma were not separated, and is virtually meaningless today.

Treatment Of Feline Lymphoma

Treatment depends on the type and location of the tumour.

High grade alimentary lymphoma, renal lymphoma and other systemic large-cell forms are treated with traditional chemotherapy protocols. These involve visits to the vet for injections, tablets and blood tests. The number and duration of visits will depend on the protocol chosen.

Nasal lymphoma is treated with similar drugs plus the use of radiation. Unfortunately, licensed radiation therapy is only available in a few capital cities. For cats in Adelaide, that means a long trip for treatment, if at all.

Small cell alimentary lymphoma is treated with alternating doses of prednisolone and chlorambucil given at home on a daily basis.

To Treat Or Not?

There is no right or wrong answer on whether to treat lymphoma in cats. However, here are my opinions based on 25 years of experience:

  1. If there’s any chance you’ll treat, don’t delay. Excessive weight loss will worsen the chance of responding to treatment.
  2. Small cell alimentary lymphoma and nasal lymphoma offer compelling cases for choosing treatment, based on their long average survival times.
  3. Other lymphomas have lower response rates: only 30% of cats achieve full remission with alimentary forms versus 52% in all other locations (remission is the disappearance of signs and symptoms).
  4. Despite this, lymphoma treatment is worth trialling to see if remission can be achieved. That’s because the survival time for a cat that can achieve remission is much better at around one year. If there is no response, or illness occurs, it’s easy to stop.
  5. Euthanasia is a reasonable and compassionate choice which cannot be criticised. Read more about taking this difficult choice here.

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By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. Meet his team here. The information provided here is not intended to be used as a substitute for going to the vet. If your pet is unwell, please seek veterinary attention.