Absolute neutrophil count (ANC): The real number of white blood cells (WBCs) that are neutrophils. The absolute neutrophil count is commonly called the ANC.
The ANC is not measured directly. It is derived by multiplying the WBC count times the percent of neutrophils in the differential WBC count. The percent of neutrophils consists of the segmented (fully mature) neutrophils) + the bands (almost mature neutrophils). The normal range for the ANC = 1.5 to 8.0 (1,500 to 8,000/mm3).
Neutrophils are key components in the system of defense against infection. An absence or scarcity of neutrophils (a condition called neutropenia) makes a person vulnerable to infection. After chemotherapy, radiation, or a blood or marrow transplant, the ANC is usually depressed and then slowly rises, reflecting the fact that the bone marrow is recovering and new blood cells are beginning to grow and mature.
In practical clinical terms, a normal ANC is 1500 or higher; a "safe" ANC is 500-1500; a low ANC is less than 500.
(Information was borrowed from medterms.com)