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LYMPHOSARCOMA (LYMPHOMA)

This information is provided by Provet for educational purposes only.

You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

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Description
A lymphosarcoma (or Lymphoma) is a form of cancer (-sarcoma) of lymphoid tissue. Lymphoid tissue is found in the lymph nodes located around the body and along the intestinal tract. 

Cause

In most situations the cause of a lymphosarcoma tumour is unknown. 

In dogs the cause of lymphosarcoma is unknown although oncogenic viruses may be involved.

However, in the cat exposure to Feline Leukaemia Virus (FeLV) can induce the occurrence of lymphosarcoma . So FeLV is an oncogenic retrovirus and the tumours that develop usually involve T-cells but sometimes involve B-cells.  The cancer cells themselves may  or may not replicate and contain the virus. FeLV can also induce myeloid and erythroid leukaemias.

In cats lymphosarcoma accounts for almost 33% of all cancers

Breed Occurrence
Siamese cats are thought to have a higher incidence of lymphosarcoma than other breeds, but there is no sex predilection. FeLV infection most often occurs in feral cats, and in households which keep a group of cats which are allowed to roam freely outside. About 50% of lymphosarcoma cases occur in cats aged only 1-3 years and a further 36% occur between 4 and 8 years of age. 

In dogs the risk of developing  lymphosarcoma increases with age and peaks at about 8-9 years of age. Boxers are thought to have an increased risk of developing lymphosarcoma compared to other breeds of dog.

Signs
 Clinical signs of lymphosarcoma depend upon the primary site of the tumour, and also whether or not it has spread to a secondary site(s). Signs include :

  • Weight loss
  • Depression
  • Lethargy
  • Fever
  • If the gastrointestinal tract is involved :
    • Thickening of the small intestine walls
    • Diarrhoea
    • Vomiting
    • Anorexia
    • Constipation
  • If the throat or chest is involved - respiratory signs may occur. In cats lymphosarcoma often affects the thymus in the chest:
    • Difficulty breathing
    • Choking or gagging
  • Solid masses may occur in tissues - eg in lymph nodes(often more than one is involved simultaneously), or skin.
  • Anaemia (reduced red cells in the blood circulation) `may occur (15-25% of dogs)
  • Leukaemia (increased lymphiod white cells in the blood circulation)
  • If lymphosarcoma affects the spine or peripheral nerves it results in neuromuscular disorders including paralysis and muscle atrophy by causing pressure on the  nerves.
  • The colour of the iris may change, retinal haemorrhages may occur or intraocular pressure may increase (glaucoma) if lymphosarcoma involves the eye.
  • If the kidneys are involved they become enlarged and renal failure (with increased urination and thirst) may result
  • Enlargement of the spleen often occurs
  • Enlargement of the liver often occurs

These signs may develop very slowly, and often lymphosarcoma is multicentirc - ie it involves more than one organ system.

Complications
 Secondary spread to vital organs may result in death or recommendations for euthanasia.

Diagnosis

The diagnosis is made by histopathological examination of a biopsy or excised "lump" eg lymph node mass. Imprint smears and aspirates are both useful. 

The normal architecture of the lymph node is lost and replaced by large numbers of lymphocytes and primitive blast cells, and these cells have a high mitotic index - ie large numbers of them are undergoing mitosis- cell division.

Treatment

Many cases of lymphosarcoma in the dog can be treated successfully with long periods of remission and increased life expectancy

There are a variety of treatments available for patients with lymphosarcoma including :

  • Surgical excision is possible when the tumour only involves one structure
  • Radiation therapy
  • Chemotherapy:
    • Often a combination of therapeutic agents is needed eg Cyclophosphamide - prednisolone - vincristine
  • Dietary management - special diets with low carbohydrate content, increased Omega3 fatty acid and arginine content. Patients with lymphosarcoma may have an increased dietary requirement for calories and protein.

Prognosis

The prognosis for patients with lymphosarcoma is always guarded or poor.

Many cats only survive for a few weeks after the diagnosis is made. However many dogs will go into remission following treatment and significant increases in survival time can be achieved.

Long term problems

Cats with FeLV virus may show few clinical signs of the disease, but they can become carriers and transmit the virus to other cats via their saliva or semen.

 

Updated October 2013

 
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