Acute Lymphoblastic Leukemia in Dogs

By Tess Thompson

Literally, leukemia means white ("leuk") blood ("emia"). White blood cells (also known as leukocytes) are actually an important part of the body’s defense mechanism, and that is the reason why the WBC count shoots up in cases of infection, allergy and stress. Leukemia is one of the four major types of cancer.

Acute lymphoblastic (lymphoblast is an immature leukocyte) or lymphocytic leukemia (ALL) is a malignant neoplasm of blood-forming tissues. It is characterized by an abnormal growth of leukocytes. The blood is flooded with a particular white blood cell. The bone marrow from where the white blood cells are produced is involved in producing cancerous cells rather than producing other blood cells that are necessary for survival.

Acute lymphoblastic leukemia is a less common type of dog cancer, and the incident of the same is relatively higher in cats (though less common as compared to lymphoma in cats).

The condition starts in the bone marrow, where an undifferentiated immature leukocyte begins to turn malignant. This single transformed cell then rapidly starts forming genetically identical cells by some kind of asexual reproduction. Acute lymphocytic leukemia (or ALL) is indicated when abnormally high numbers of lymphoblast, as high as or more than 100,000 (3500 is normal in dogs), are seen in the bone marrow and an increased number in the blood.

Clinical signs like lethargy, eating disorders, diarrhea, vomiting and a general loss of vitality are confusing, as these symptoms are similar to symptoms of various other diseases, as well. However, there are some other symptoms that can be considered as a confirmation of a more serious condition. These are:

  • Inflammation and abnormal enlargement of spleen, liver and lymph nodes
  • Paling of mucous membranes
  • Minute red or purple spots on the surface of the skin (as the result of tiny hemorrhages of blood vessels)

The exact cause of ALL in dogs has not been established. Some believe that the condition can be caused due to toxins or specific dog ailments that lead to abnormal proliferation of immature lymphoblast-like cells in bone marrow. Exposure to radiation and benzene has been linked to ALL in humans, and there is a strong possibility that similar factors affect dogs as well. In cats, however, the feline leukemia virus is involved in development of the condition.

The prefix ‘acute’ in the case of leukemia has nothing to do with the normal understanding of the term (a sudden development of a disease). The acute condition in this case refers to abnormal multiplication of immature leukocytes and chronic conditions to that of developed cells. Acute lymphoblastic leukemia is more malignant than chronic. Prognosis for dogs with this type of fatal cancer in dogs is very poor. Even aggressive chemotherapy, patients of ALL are not likely to survive for more than a few months after diagnosis. Without treatment, the survival time is only a few weeks.


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