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Histology is a science that studies the composition and structure of tissues in living organisms in relation to their specialized functions. This discipline is necessary for the understanding and development of biology, medicine, veterinary medicine.
Histopathology is the diagnosis and examination of biological tissues in order to observe the appearance of diseased cells and pathology in tissues in great detail under a microscope.
What is a histologist
Accordingly, a histologist or histopathologist is a doctor who examines the structure of tissues in a living organism, diagnoses and studies the disease, using the interpretation of cells and tissue samples of human organs.
It is his work that is an integral part of the fight against cancer, through the correct diagnosis and classification of the tumor.
It is he who studies the materials taken during various operations, scrapings during examination by a gynecologist, a small amount of tissue or fluid taken during a biopsy of tumor diseases. It can also examine sputum cells and various fluids from the pleura, effusion, or abdominal fluid.
Histopathologists are responsible for making diagnoses after tissue examinations and are of great help to clinicians in the treatment of patients. After all, they work closely with other clinical specialties such as gynecologist, oncologist, surgeon, neuropathologist and many others.
What skills should you have
Physicians in this specialty must be attentive to detail for tissue examination and disease diagnosis. After all, many of them look very similar, so it is important to identify small, but differences. They must be able to work clearly and quickly, often making critical decisions every day, as the interpretation of what they see under the microscope will determine what treatment the patient should receive.
Histopathologists must be highly motivated and able to work both independently and as part of a team. Good communication skills are essential to discuss the relevance of microscopic data with fellow clinicians. Good diagnostic skills are very important in order to determine not only the type of disease, but also its severity and extent, which is necessary when choosing a treatment.
Why do a histological examination?
The method of histological diagnostics is actively used to determine the causes of infertility, diseases of the endocrine glands, inflammation of internal organs, and precancerous diseases. It is also carried out to identify the early stages of cancer development in gastritis, ulcers, to establish the degree of liver damage.
Diagnostics of biopsy specimens of human organs is carried out in order to determine changes in the structure and structure of tissues and cells in various pathologies.
And also to:
- determine the volume and radicalness of surgical intervention;
- study the assessment of the quality of the treatment or the rate of development of the disease;
- determine the nature, form, degree or stage of the pathological process (inflammatory, tumor: malignant or benign);
- early detection of the disease, before the appearance of patient complaints.
This study is most often used to diagnose cancer. Indeed, without it, oncologists will not be able to conduct the correct treatment. Histologists process cells and tissues removed from suspicious “lumps and bumps”, identify the nature of the pathological process. If they are malignant, they provide the clinician with information about the type of cancer, its stage, and, for some tumors, their response to certain treatments.
New techniques, such as fluorescent in situ hybridization and polymerase chain reaction (PCR), are now widely used in European countries to display genetic material in tumor tissues, which are necessary for the treatment of many types of cancer.
Types of samples for detailed study
The laboratory receives materials for diagnostics, which are taken when a specific organ or neoplasm is punctured with a thin needle for research, also called a puncture biopsy.
These are liquid or very small pieces of tissue, more often single cells rather than groups of cells, for example, a tumor formation of a lymph node.
Since the doctor can only take a small part of it, there is a high probability that the area with the pathological focus will not fall into the area taken. Then it will be necessary to carry out a repeated puncture biopsy.
Examples of biopsy examinations include endoscopy (eg, examination of the esophagus and stomach) or colposcopy (examination of the cervix with a magnifying instrument). An example of a more organized procedure is the kidney biopsy, where a piece of tissue is obtained by passing a needle through the skin and into the kidney.
Usually, little information can be obtained by looking at this biopsy specimen with the naked eye, and key information is obtained only under a microscope. Many biopsies are reassuring because they were done to rule out cancer. And it does not confirm cancer, but it can, for example, show inflammation, which explains the clinical symptoms and signs in the patient. Other biopsies may show abnormal cells, and the histologist is looking for signs that tell which cancer is present, how advanced it is, and whether it will respond to certain treatments.
In addition, samples that are removed during surgery will be placed on the laboratory table. It can be either a whole organ or a neoplasm, or a small section of them. Examples include the uterus after a hysterectomy, the colon after a colectomy, or the tonsils after a tonsillectomy. The pathologist carefully examines these samples with the naked eye and cuts off small pieces of tissue for examination under a microscope for more detailed examination. Require less surgical procedures, can be performed without anesthesia, sometimes with the use of a soothing injection cervical scraping, from the uterine cavity, cervical biopsy, various skin diseases.
An urgent study can also be carried out when the material is obtained at the time of the operation in order to know how to proceed further for successful treatment. This should be done in no more than 20 minutes.
The surgeon removes a small amount of tissue and waits for the histologist to draw conclusions and make a diagnosis before deciding how to proceed.
The patient is asleep under anesthesia while this is happening and knows nothing about it. Quite often, histologists bring good news, for example, by discovering that a part of the organ being examined is completely benign and there is nothing to worry about.
Preparation of biopsy material
Probably many patients and even doctors asked themselves the question: “I wonder what is happening with my biopsy right now?”. The process that virtually all samples go through is described below.
The first step is fixing the tissue. Slides preparation starts with fixing your sample. This is important in tissue preparation and the purpose of this is to prevent tissue autolysis and putrefaction. For best results, biological tissue samples should be fixed immediately after collection. This works best in 10% neutral buffered formalin.
The optimal volume ratio of formalin to sample should be at least 10:1 (for example, 10 ml of formalin per 1 cm3 of tissue).
This will allow most tissues to become adequately fixed within 24-48 hours. Formalin containers must be sealed and properly labelled.
The second step is transferring the material to cassettes. After fixation, the specimens are trimmed with a scalpel so that they can fit into the corresponding labeled tissue cassette. They should not be so large as to fill the entire cassette – they are cut off so that they do not touch the edges. In addition, test materials should not be too thick (ideally less than 4 mm), otherwise they risk becoming “wafer” when the cassette lid is closed. The filled tissue cassettes are then stored in formalin until processing begins.
Step three – fabric processing. It can last from four hours to thirteen hours depending on their size. Tissue processing already in thin microscopic sections is usually carried out using a special block as follows. Alcohol slowly dehydrates the fabric, removing water and formalin from it. Xylene, an organic solvent, removes alcohol from fabric. Paraffin wax replaces xylene and permanently penetrates the fabric. The plastic cassettes containing the tissue pieces are then transferred. The tissue is removed from the cassette and placed in a mold which is then filled with liquid paraffin. Then the part of the cassette on which the patient’s hospital number is printed is placed on top of the form. After cooling, the top of the cassette and the paraffin-embedded tissues become one unit, known as the paraffin block.
The fourth step is the separation of thin sections of biopsy tissue into glass slides. The paraffin block is then transferred to an instrument known as a microtome. The block is placed in a holder, which is then passed through the blade. Each time the block passes the blade, it advances three or four micrometers. This is approximately the thickness of one tissue cell.
As the tissue continues to pass through the blade, several sections of it are reproduced in a long ribbon. This tape is picked up by a laboratory assistant and floats in a bath of warm water. When all the irregularities are smoothed out, the histologist takes them out of the water. A slide with a very thin section of paraffin and tissue is the result of a microtomy.
The fifth step is coloring. Most cells are transparent and appear almost colorless when not stained. Two staining reagents are used – hematoxylin and eosin. Hematoxylin stains the nucleus of tissue cells from dark blue to black. And eosin stains the inside of the cell, surrounding the nucleus, in a light pink color, and the tissue outside the cell from dark pink to red. This makes tissues more visible and easier to assess cellular composition.
It can be concluded that a histologist confirms or refutes various diseases in the human body that were diagnosed by other clinicians. Without its final diagnosis, doctors cannot prescribe the correct and effective treatment. That is why the work of a histologist is very important and responsible for medicine today.