The Difference Between Acute and Chronic Leukemia

If I never teach you anything else, please let me teach you how important this is:

…The difference between acute leukemia and chronic lymphocytic leukemia.


Because the prognosis is HUGELY different between the two, and evaluating the blood smear is VITAL in differentiating them!

Dogs with acute leukemia are clinically sick, and their median survival time is terrible.

Dogs with chronic lymphocytic leukemia are typically clinically normal (often is picked up on yearly blood work incidentally), and the median survival time is actually pretty good. I’ve seen dogs live 2+ years with CLL and die of completely unrelated old-dog diseases.


On the blood smear, acute leukemia looks like a bunch of large, immature cells. CLL looks like a bunch of well-differentiated small lymphocytes.


So, the next time you see a patient with a lymphocytosis on its CBC, even if you’re sure it’s a neoplastic process because the number is out of this world, you MUST look at the blood smear, or you don’t have all the information you need*. 

*sometimes morphology isn’t always clear/straightforward and you need additional testing with tests like flow cytometry to confirm/determine the type of leukemia