Vacuoles are colorless bladder-like recesses in the cytoplasm or nucleus of the cell and contain accumulated material (waste). Vacuoles are a sign of increased metabolic or phagocytic activity and are often accompanied by other toxic abnormalities such as hypergranulation and bodies of döhle.

Vacuoles can also form as artifacts in old material due to contact with EDTA, in which case other toxic characteristics are absent and the vacuoles are often small and uniformly distributed.