Canine Lymphoma(Lymphosarcoma)

Lymphoma represents a common neoplasia of dogs affecting the entire 
lymphatic system including the spleen, thymus and liver.  The cause of 
canine lymphoma is unknown however there are known viral causes in other 
species such as the feline. There is no predisposition for lymphoma but, 
there are higher numbers in the German Shepherd and Boxers. The disease 
affects primarily middle age to older animals but can occur in younger 
dogs.

The disease usually described by location of the tumor ie., Multicentric 
or nodal (Peripheral lymph nodes and usually includes liver and spleen), 
Alimentary( Gastrointestinal tract), Mediastinal( Lymph nodes within the 
mediastinum),  and Extra Nodal.  Extra nodal forms of lymphoma are less 
common. They involve non lymphoid tissues such as bone, eyes, brain, 
heart , white blood cells (leukemic), skin, kidneys etc. Extranodal forms 
account for a minority 
(less than 15%) of lymphomas.

In addition,  the World Health Organization stages lymphoma by the extent 
of the disease:
	Stage 1. limited two one node or organ
	Stage 2. Involvement of many nodes in a region
	Stage 3. General node involvement
	Stage 4. Liver or spleen plus or minus stage 3
	Stage 5. Metastasis to bone marrow with or without  Stages 1-4

Signs of Lymphoma will vary depending on the location of the tumors. 
Often dogs are presented with non specific signs. However, most lymphomas 
are associated with anorexia, GI upset and weight loss. Often lymph node 
enlargement is palpable. Some dogs are presented with signs of liver 
failure which can include jaundice and anemia.

A diagnosis is made with a biopsy of a lymph node, spleen or liver for 
histopathology. Staging the extent of lymphoma involves hematology, blood 
chemistries, bone marrow aspirates, radiographs and ultrasound. 

Therapy for nodal lymphomas are well described and available to the 
practitioner in the field. Success for remission with chemotherapy is 
very good and the quality of life remains excellent. Success rates are a 
function of tumor location. Bone marrow involvement has a poorer 
prognosis. Remissions for nodal forms of two years or more are possible. 
Side effects of chemotherapy found in human patients are often absent in 
the dog. However, evaluation of hematology parameters are important to 
monitor toxicity. Without therapy most lymphoma patients succumb within 2 
months of the diagnosis. Therapy for extranodal lymphoma usually requires 
surgery, chemotherapy and, or radiation with follow up diagnostics 
checking for reoccurrence. Success is dependent on the location of the 
extranodal lymphoma.