From Dog

Lymphocytosis in dogs is defined as a marked elevation in circulating levels of lymphocytes > 4.8 x 109/L.

Although this is usually interpreted as an infectious response by the lymphocytes, other causes may be present, including:

- Lymphoma, leukemia, thymoma
  • Stress response

Persistent lymphocytosis of small, mature, or reactive lymphocytes is most commonly the result of chronic lymphocytic leukemia or lymphoma[1].


  1. Avery AC & Avery PR (2007) Determining the significance of persistent lymphocytosis. Vet Clin North Am Small Anim Pract 37(2):267-282