A leukemoid reaction is an increase in white blood cell count similar to what occurs in people with leukemia. However, the reaction is actually due to an infection or another disease and is not a sign of cancer.
Blood counts will usually return to normal when the underlying condition is treated.
Bagby GC. Leukopenia and leukocytosis. In Goldman L, Ausiello D, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011: chap 170.