Lymphoid leukemias are rare malignant cancers that originate from the white blood cells in the bone marrow.

Acute lymphoid leukemias have immature (blast) cells in the blood stream and/or bone marrow.

Common signs seen by pet owners lethargy, not eating, weight loss, shifting leg lameness, fever, vomiting and diarrhea.

Treatment requires aggressive chemotherapy (vincristine and prednisone) with few patients successfully going into remission.

What is Canine Lymphoid Leukemia?

• Lymphoid leukemias are rare malignant cancers that originate from the white blood cells in the bone marrow.
• Instead of maturing into normal cells, these precursor cells divide and replicate in an immature and non-functional form.
• These cells may be found circulating in the blood stream and/or in the bone marrow.
• Lymphoid leukemia can be classified by whether they appear in the blood stream or only appear in the bone marrow. They can be further classified as acute or chronic based on the biological behavior and timeframe of the disease.
• Acute lymphoid leukemias have immature (blast) cells in the blood stream and/or bone marrow.
• They are very aggressive in nature, divide rapidly, and without treatment death occurs shortly after diagnosis.
• Some of the known causes of leukemia include radiation exposure and some viruses, but they are known to spontaneously develop too.

Clinical Signs

• The clinical signs of Lymphoid Leukemias are often vague and non-specific.
• There is no known breed or sex predilection.
• The age of disease onset varies widely with ranges from one to twelve years of age and with medians around 5.5 years old.
• Common signs seen by pet owners lethargy, not eating, weight loss, shifting leg lameness, fever, vomiting and diarrhea
• Common signs seen by your veterinarian
  • increased liver or spleen size (hepatomegaly or splenomegaly) mild increases in the lymph node size (mild lymphadenopathy)
  • pale mucous membranes
  • fever
  • bruises along the gums (petechiae)
  • changes in the eyes (ocular lesions)
  • lameness and/or neurological signs
  • patients are often clinically and critically ill

Diagnosis

• The diagnosis of acute lymphoid leukemia is made by clinical signs and laboratory tests.
• The most common tests used to confirm leukemia are: complete blood count (CBC) – This is to determine the number and percentages of each type of cell in the blood. In leukemia abnormal cells are often seen in the circulation and increased numbers of lymphocytes are often seen. Additionally, the leukemia can cause decreases in other cell lines like red blood cells (anemia) and platelets (thrombocytopenia). Routine blood work on pets with leukemia will often show decreases in red blood cells or platelets ( cytopenias or pancytopenias). They often show a marked increase in the circulating lymphocytes, often over 20,000 and numerous blast (immature) cells.
• Bone marrow aspirate – This will determine if abnormal numbers of immature lymphocytes are present in the bone marrow. In cases of some leukemias, the abnormal cells may only be present in the bone marrow and not seen in circulation on the CBC.
• Fine needle aspirate of spleen or liver if enlarged – If the organ enlargement is caused by infiltration by the lymphoid cells, then this may be found on cytology of the organs aspirated.
• Serology to rule out other causes of an increased white blood cell count – Often blood work is performed to look for other causes of an increased white blood cell count (infectious diseases). These tests are used to look for more easily treatable diseases that have similar clinical signs and laboratory results. Other causes with similar clinical signs and blood work values include infectious diseases ( rickettsial diseases and hemobartonella) and other types of cancer ( lymphosarcoma, lymphosarcoma cell leukemia, histiocytosis, mast cell leukemia).
• Cytochemical staining – These are special stains performed on the blood or bone marrow to determine the origin and type of leukemic cells. This may be used to verify the disease or may change the prognosis or treatment.

Treatment

• Acute lymphoid leukemias carry a very grave prognosis and usually do very poorly even with treatment.
• Treatment requires aggressive chemotherapy ( vincristine and prednisone) with few patients successfully going into remission. The median survival time with remission is approximately 3-4 months and without treatment or remission approximately 1-2 weeks.
• Treatment failures most often occur due to failure to induce remission, due to organ failure from leukemia infiltration, or due to fatal sepsis or bleeding from the cytopenias.

Complications

• Side effects from the medication used to treat leukemia may include:
  • bone marrow suppression with increased risk of anemia, infection, and bleeding
  • nausea
  • liver toxicity
  • skin necrosis if the intravenous injection of vincristine leaks outside of the vein

Prognosis

• Acute lymphoid leukemia carries a very poor prognosis with median survival times numbering in days without treatment.
• Even with treatment the prognosis is very poor with survival times in the 3-4 month range.