CANINE LYMPHOSARCOMA – CANINE CANCER

CANINE LYMPHOSARCOMA (Lymphoma, LSA) CANINE CANCER

INCIDENCE/CAUSE
LSA, a tumor caused by a cancerous proliferation of lymphocytes (cells that normally function in the immune system), is one of the most common tumors seen in dogs. It affects dogs of any breed and age, although most dogs will be middle-aged or older at the time of diagnosis; Golden retrievers are considered a breed at increased risk of developing LSA. The cause of LSA in dogs, as is true for most canine tumors, is not known.

WHAT YOU MIGHT SEE/ CLINICAL PRESENTATION:
The presentation of dogs with LSA is highly variable as lymphocytes can be found in virtually any organ in the body. Nonetheless, the most common form (referred to as stages) of LSA causes a non-painful enlargement of one or more lymph nodes that can be seen or felt from the body surface. Occasionally, a lymph node becomes large enough to impair function (obstruction of blood flow or airway, for example). Other forms of LSA can involve the liver, spleen, bone marrow and gastrointestinal tract, skin or nervous system (and other organs) and the clinical signs will reflect the organ system involved (e.g. vomiting or diarrhea with gastrointestinal forms; weakness or pale mucous membranes and others that reflect impaired production of blood cells from the bone marrow); many dogs will simply feel ill (lose appetite, become lethargic) with any of the different forms. In some dogs, lymph node enlargement is an incidental finding when an otherwise healthy-appearing dog is seen by a veterinarian for an unrelated reason (e.g. vaccination).

LYMPH NODE STAGING
Stage I: single lymph node enlarged
Stage II: multiple nodes enlarged on either the front half or back half of the body
Stage III: multiple nodes enlarged on both front and back halves of body
Stage IV: involvement of the liver and/or spleen
Stage V: bone marrow involvement, or involvement of other organs (e.g. gastrointestinal, skin, nervous system)
Each numbered stage can be further divided into substages, of which there are two: a and b. Patients with substage a feel well while patients with substage b are ill.

BIOLOGICAL BEHAVIOR OF LSA
LSA is viewed as a systemic disease, and as such is not really viewed to “spread” to other organs. This tumor is not generally viewed as a curable tumor in dogs, although occasional dogs will experience what seems to be a cure with appropriate treatment (see below). A dog can start with one stage of the disease and progress over time to another (usually more advanced) stage of LSA..