The main stages of histological examination:
- "Tenderloin" - a pathologist excises small pieces (1x1x0.5 cm) from an object delivered to the laboratory for examination. At this stage, it is very important to thoroughly examine the object "by eye", analyze its appearance and interaction with neighboring tissues, which will significantly affect the result of microscopic examination and the completeness of the answer to the questions posed to the specialist.
- "Histological wiring" is the processing of a piece: fixation, dehydration, and paraffin impregnation. Since the human body consists of 80% water, and its tissues are mostly soft or, conversely, too dense, it is very difficult to prepare a thin slice directly from it, while preventing natural spoilage (swelling). For these purposes, first of all, the so–called fixation of the piece is carried out (essentially, canning) – this is done with the help of fixatives - usually liquids, such as formalin, which is not only the strongest poison for microbes, but is also able to preserve tissues for a long time.
- "Filling" - a piece of cloth soaked in paraffin is filled with paraffin, a paraffin block is formed. Paraffin is insoluble in water, while the human body, on the contrary, consists almost entirely of water. Therefore, the piece under study is dehydrated, and already in this state it is soaked in hot paraffin, which, after solidification, is a very convenient block for subsequent processing. The quality of such a block will depend on how evenly the piece was soaked. For better processing, basic knowledge of physics can be used: processing in a solution jet, increasing and decreasing pressure – which is available only with modern specialized equipment.
- Microtomy is the preparation of ultra-thin sections 3-5 microns thick from a paraffin block, followed by their transfer to a slide. It is this thickness that allows the cells not to overlap each other, and the light rays in the microscope can easily pass through them. This block is cut on a special device – a microtome. Moreover, the thinner the slice, the higher the quality of the final product. Obtaining ultrafine slices is possible only if modern digital technology is available.
- Microsection staining is performed by a laboratory technician in a histological laboratory. The range of dyes is very wide, and preparation for staining is often individual in nature and requires in–depth knowledge of the chemistry of solutions and tissues of a living organism: some dyes interact with cell nuclei, others with cytoplasm, others stain fat, others mucus produced in the stomach, etc. A laboratory technician must have not only a set of technical skills in order to to preserve the material with minimal changes, despite a series of aggressive liquids, but also to understand the tasks assigned to the doctor in order to present the extracted pieces in the most informative way. The result of the work is significantly influenced by the technical equipment of the laboratory. The introduction of modern equipment allows not only to increase the quality several times, but also to bring it to a single standard. The result of the laboratory technicians' work is a histological preparation (slide).
- The examination of micro-preparations under a microscope is carried out by a pathologist, who also makes a histological diagnosis based on the observed changes. A doctor is required to have a detailed knowledge of tissue and cellular structures, their mutual influence not only in a healthy body, but also in various diseases, including cancer.
The result of the work carried out is a histological conclusion (histological diagnosis), which gets to the attending physician and to the patient's medical history. Based on this conclusion, it is determined whether the disease is cancerous, whether it poses a threat to life, and what treatment tactics to choose.
