Vacuoles are areas of the cytoplasm that do not stain with Wright's stain and appear as holes in the cytoplasm. Their composition may vary; some contain remnants of bacterial digestion or autodigestion in an aging cell, while others contain fat. It is impossible to differentiate the various types of vacuoles on Wright-stained smears using light microscopy.
Vacuoles may be seen occasionally in an aging granulocyte (degenerative vacuolation), but they are more frequent and significant in cases of bacterial infection and septicemia.
