Occasionally, stain is not completely washed away during the staining process. Artifact can remain, and occasionally can be confused with pathology. Focusing in and out will reveal that the debris is on a slightly different focal plane than the cells.

Cellular debris, including nuclear remnants, cytoplasmic remnants and granules, can remain following a cell rupture.

Ruptured cells leave debris on the smear that will pick up stain.

Contamination of the fixative with water can produce refractile ‘water artifact’ on slides. Slides should be completely dry before staining