Cautery artefact is the term used by pathologists to describe how heat changes the way cells look when examined under the microscope.
Electrocautery is commonly used during surgical procedures. Electrocautery stops bleeding by heating the tissue and clotting the blood. When examined under a microscope, cautery artefact causes the body of the cell to look pinker (eosinophilic) and the nucleus of the cell to look darker (hyperchromatic) and stretched out compared to normal cells.
These changes can make it difficult for a pathologist to decide if any other disease-related changes are also happening in the tissue.