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Artifacts in Pathology

Updated: Oct 14, 2022

There is no cultural or historical aspect of an artifact found on a pathology slide. However, like a historical artifact, a pathologist has to unveil its true origin and circumstance. In anatomic pathology, we define an artifact as anything causing difficulty in interpreting the specimen on the slide other than the inherent complexity of the disease process. This can range from the desiccation of the tissue to the presence of alien tissue fragments, “floater” in pathology lingo. There are several steps from the start of the biopsy procedure to its presentation on the slides. Any of these steps can produce artifacts and make the patient’s diagnosis and pathologist's license in jeopardy.

The artifacts can be divided chronologically into three major categories according to the site of occurrence:

1- In the Doctor's office

During numbing

  • An anesthetic agent in the lesion can cause tissue displacement and alter the microscopic architecture.

during numbing

During procedure

  • Instruments

    • Crush artifacts and teeth marks caused by tightly held forceps or blunt a blade. If significant, they can render biopsy nearly unreadable.

  • Fulguration

    • artifact caused by the use of a hot knife or cautery. The heat alters the cellular and connective details. Epithelial cells assume a spindle appearance with a loss of cellular details. Collagen and elastic fibers coagulate into clumps leaving empty spaces.

  • Hemorrhage

    • Excessive bleeding into the biopsy tissue can mask the pathology or cause confusion with pathologic hemorrhage caused by vascular or coagulation disorders.


2- In Transportation


  • 10% formalin freezes at temperatures lower than 12 F, creating crystals in the tissue and a “Swiss cheese appearance.” Leaving biopsies overnight in drop boxes in winter is, therefore, best avoidable.


  • Tissue may move out of the fixative, causing autolysis.

3- In the Laboratory

Grossing station

  • Floaters are tissue fragment that does not belong to the biopsied tissue.

    • They may accidentally be introduced in the cassette by the forceps or blade if there are not thoroughly cleaned after every specimen.

Tissue processor

  • Tiny floaters may also be introduced from other cassettes within the processing chamber.

  • Fixation issues may arise due to the wrong program, processor malfunction, or chemical expiry.

Embedding station

  • Tangential artifact

    • Embedding is orienting the tissue in the block so the desired surface is parallel to the microtome blade. If the tissue moves before the wax solidifies, it will be cut at a tangent creating a tangential artifact. Tangential sectioning can make the lesion look more atypical than it is.

  • Faulty embedding may also lead to loss of structure to be examined, e.g., partial or complete loss of the epithelium to be studied.

Embedding station


  • Microtomy can produce a number of artifacts depending on the angle of engagement of the blade and the block. Angle variations can cause section thickness variability, curling, or discohesion of ribbons.

  • A dull or nicked blade leaves streaks and spaces in the sections.


Tissue bath

Remnants from an earlier specimen in the tissue bath can be picked up on the slide.

Tissue bath


Precipitation of staining particles occurs if the staining chemicals are not dissolved properly or if the stain is not fresh. The precipitation can make slides difficult to read. Artifactual pigment deposition can also occur if acid formaldehyde reacts with hemoglobin to form acid formaldehyde hematin pigment.


Cover slipping

Slides can have masking air bubbles by improper coverslipping.

Cover slipping

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