Feline Lymphoma

Lymphoma is one of the most common forms of cancer in cats, accounting for around 1/3 of all tumours. Lymphoma is one of the most common forms of cancer in cats, accounting for around 1/3 of all tumours. The tumour cells originate and proliferate from both B and T lymphocytes in the bone marrow, lymph nodes and visceral organs. As a result, lymphoma can appear almost anywhere affecting vital organs such as the liver, kidneys and gastro-intestinal tract.

Posted: 02 May 2019

Feline Lymphoma

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5 Forms of Feline Lymphoma

1. Alimentary

– this form of lymphoma affects the gastrointestinal tract, abdomen, liver and surrounding lymph nodes. It’s the most common form of feline lymphoma but is also the least likely to be associated with the Feline Leukaemia Virus (FeLV).  Signs to look for include;

  • Anorexia
  • Lethargy
  • Vomiting
  • Constipation
  • Diarrhoea
  • Black or tarry faeces
  • Fresh blood in stools

2. Multicentric

– this form of feline lymphoma is closely associated with FeLV. It generally involves multiple lymph nodes and organs.  Unfortunately, the prognosis is poor if the cat is FeLV positive. Look for;

  • Swollen lymph nodes
  • Loss of appetite
  • Weight loss
  • Depression

3. Mediastinal

– this form of lymphoma affects the thymus and associated lymph nodes. Like the multicentric form, it can also be linked to FeLV. Typically, there will be a mass in the pleural cavity. Signs include;

  • Open mouth breathing
  • Cough
  • Anorexia
  • Weight loss

4. Renal

- this is the most common renal tumour in cats and often presents with sudden onset renal failure. A clinical examination will show;

  • Anorexia
  • Vomiting
  • Weakness
  • Polyuria and polydipsia
  • Bilaterally enlarged and irregular kidneys

5. Ocular

– this can be both unilateral or bilateral and can precede the onset of systemic lymphoma. All parts of the eye and retrobulbar space can be affected, with the uvea being the most commonly affected site. Signs may include;

  • Uveitis
  • Iritis
  • Miosis

Categorising lymphoma helps determine the prognosis

Lymphoma can also be categorised according to the type of neoplastic lymphocyte cells. Broadly speaking they are divided into two main types;

  • High grade (or large cell) lymphoma
  • Low grade (or small cell) lymphoma

These two types of lymphoma vary in behaviour, so it’s important to make a precise and definitive diagnosis to allow you to make the right choice of treatment. The grade of tumour will also affect the prognosis.

Making a diagnosis

This is best achieved using a combination of blood tests and imaging procedures.

Routine blood tests would include haematology (red and white cell counts), biochemistry and electrolytes. Urinalysis is also of value. Look for;

  • Anaemia – this is as a result of the neoplasia itself, but may also be linked to the cat being FeLV positive
  • Lymphoblasts – these are immature cells which differentiate to form mature lymphocytes. They are normally present in the bone marrow, but if they proliferate, they may migrate to the peripheral blood, resulting in the abnormal condition called lymphoblastosis 
  • Elevated biochemistry – check for high creatinine, serum urea nitrogen, liver enzymes and calcium (lymphoma is the most common cause of hypercalcemia in cats)
  • Urinalysis – check for elevated urine bilirubin and proteins
  • Test for FeLV – exposure to the virus will potentially result in development of the multicentric and mediastinal forms of lymphoma. A positive FeLV test should make you suspicious

Other investigations would include biopsy, radiography, ultrasound and CT. Fine needle aspirates or biopsies are often absolute and diagnostic.

What treatment is available?

A. High grade lymphoma

Chemotherapy – this is often the treatment of choice, frequently given in combination with surgery or radiotherapy. There will be some cases which are amenable to surgery, where a mass can be resected (for example an obstructing mass in the small intestine) and removed prior to starting chemotherapy.

Some of the drugs used include;

  • L-asparaginase
  • Doxorubicin
  • Cyclophosphamide
  • Vincristine
  • Prednisone

The aim of chemotherapy is to induce remission by destroying most of the cancer cells.  This is achievable in 50-75% of cats. Even those cats that don’t go into remission will often feel better for a reasonable period of time. The average survival for cats in remission is between 6 and 9 months, though in a small number of cases they may be in complete remission for more than 2 years. The length of remission will depend on several factors, such as;

  • The primary site of the tumour
  • How unwell the animal is prior to treatment
  • How quickly the tumour is diagnosed
  • The feline leukaemia status. Those that test positive for FeLV have a poor prognosis

Eventually, the animal will come out of remission as the cancer cells return. At this stage, the chemotherapy protocol is often changed to introduce new drugs, but in time the animal will no longer respond to therapy.

Did you know…?

  • Chemotherapy increases the chances of long-term survival and extends the quantity and quality of life.
  • The average survival time with no chemotherapy is just 4 weeks.
  • Surgical removal alone will not be curative. 
  • Surgical removal does not significantly add to the survival time achieved by chemotherapy.  It is rare to cure lymphoma. 
  • Cats treated with prednisone alone will have a life expectancy of 60-90 days.

B. Low grade lymphoma

These are frequently found in the gastrointestinal form of lymphoma. They tend to be slow growing and may require surgery if causing an obstruction. Chemotherapy is often used, and in these cases we tend to use chlorambucil and prednisolone.

Most cats will show a good response to to treatment (85-90%) within just a few weeks. The survival times of cats that are treated with low grade lymphoma is between 1 and 2 years.

The chemotherapy dilemma

Before embarking on any chemotherapy for lymphoma, it’s essential you discuss all aspects of the medication (especially the side effects) and likely outcome with the owner. It’s so important to remind them that;

  • A cure is unlikely
  • The aim is to achieve quality of life for as long as possible
  • You need a tolerant cat as not all patients are the same
  • Success depends on many factors – e.g. the stage of the lymphoma, age of the cat
  • Surgery may be required as well as chemotherapy and radiotherapy
  • Addition treatments may be necessary – e.g. analgesia

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