In some cats, the blood will be full of immature white blood cells called lymphoblasts. (1800petmeds.com)
For example, the presence of increased numbers of immature white blood cells, called band neutrophils or bands for short, indicate a serious infection. (amcny.org)
In both acute and chronic myelogenous leukemia, immature white blood cells in the bone marrow multiply out of control. (discovermagazine.com)