The Facts

• Lymphocytes are white blood cells, part of a dog's autoimmune response system, often divided into two groups: B-cells and T-cells. Prolymphocytes are immature lymphocytes not yet ready for distribution in the blood. Lymphoma is a malignant tumor appearing in lymph nodes throughout the body, often as a solid mass. In PLL, too many prolymphocytes are measured in the blood and bone marrow.
  
  

Significance

• Dogs are companion animals to humans and face the same influences from the environment as their owners. Studying prolymphocytic lymphoma and canine leukemia in dogs can help scientists understand the disease in humans and help in finding a cure for dog and human alike.
  
  

Types

• Both B-cells and T-cells can develop into PLL. Both REAL (Revised European-American Lymphoma Classification) and WHO (World Health Organization) classify T-PLL as peripheral T-cell neoplasms (abnormal growth of tissue or "tumor"). REAL and WHO both classify B-PLL as peripheral B-cell tumors. B-cell cancers are more common than T-cell cancers. PLL progresses faster than chronic lymphocytic leukemia (CLL).
  
  

Causes

• Chromosomal abnormalities such as Ataxia telangiectasia (AT) can make an individual dog more susceptible to prolymphocytic lymphoma.
  
  

Identification

• Prolymphocytic lymphoma is diagnosed if over half the leukemia-affected cells are prolymphocytes rather than mature lymphocytes.
  
  

Treatment

• B-cell and T-cell prolymphocytic lymphomas are rare, but are considered to be incurable. Treatment of the disease focuses on making the patient comfortable. As of 2009, chemotherapy and radiation may halt the progression of the disease but cannot cure it.
  
  

Expert Insight

• In 2002, studies were conducted at the Laboratory of Hematology-Cytology-Immunopathology, National Veterinary College in Lyon, France, that showed a small category of clear-cell lymphomas in dogs differed from T-PLL lymphomas in humans. In dogs, the cells did not progress rapidly into leukemia as they did in human statistics, and there seemed no direct corollary in human T-PLL.