Artifacts during histological examinations

histological examination of biopsy and postoperative material is a very important stage in the correct diagnosis and further treatment of the patient in our era of personalized medicine. Morphological diagnostics helps to establish the correct diagnosis, determine and correct further tactics of therapeutic or surgical treatment of the disease, and identify the prognosis of the course of the disease. In addition, the modern branch of pathological anatomy includes a wide range of additional studies, such as immunohistochemical, molecular genetic, the conduct of which requires the provided biological material to carefully follow standard operating procedures when working with samples. The produced histological preparations must be of extremely high quality and provide an opportunity to accurately assess all important changes presented in the biological material, since not only the microscopic visual assessment of the sample and its morphological changes are important, but also the molecular genetic structure of the tissue. Therefore, any factors that may affect the quality of the histological preparation should be controlled by developing and adhering to standard operating procedures for working with laboratory equipment, chemical solutions, performing work in the correct sequence and with strict timing, detailed study of instructions and training of personnel. Depending on the type and severity, histological artifacts can reduce the diagnostic value of biological material and even lead to partial or complete loss of the diagnostic value of the sample, which can lead to inaccuracies in establishing the diagnosis and, above all, the need to repeatedly expose the patient to risk during the material collection procedure. The relevance of this literature review is due to the multi-stage production of histological slides and the high responsibility of this work due to its significance for the subsequent therapeutical ("therapeutic")and diagnostic process. Often, the collection of biological material for pathomorphological examination from a patient carries certain health risks, since the collection procedure may include narcosis, analgesia and invasive surgical procedures. Our work analyzed the data of many authors of articles, training materials, protocols on the most frequent causes of histological artifacts and methods for their avoidance. The classification of the most common artifacts includes: prefixation artifacts, artifacts of fixation, histoprocessing, embedding, microtomy, staining. Prefixation artifacts occur most often at the preanalytical stage of biological sample collection due to manipulations with it by clinical department employees. Fixation artifacts are the result of an incorrectly selected fixation solution, its concentration and timing. Histoprocessing artifacts include a very wide range of problems that arise due to the incorrect sequence, specificity of reagents, timing, which are necessary at the stage of histological recording of a biological sample. Embedding artifacts occur with incorrect orientation of the sample, when choosing a poor-quality embedding medium and careless manipulations during this process. Microtomy artifacts are the result of using poor-quality microtomy blades, improper microtomy procedure, contaminated aqueous medium of wet microtome, contamination of microtome with microorganisms. Staining artifacts occur when timing and sequence of staining of the specimen are not followed during manual or automatic staining, as well as the use of poor-quality, dirty dyes and chemical solutions. Coating artifacts are usually the result of air entering under the coverslip and the use of too thin and poor-quality mounting medium. Internal algorithms of the histology laboratory should include assessment of the quality of the prepared histological preparations, mechanisms for controlling the occurrence of artifacts and their prevention.