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, and veterinary medicine.
Histopathology is the diagnosis and examination of biological tissues in order to monitor the appearance of affected cells and pathology in tissues in great detail under a microscope.
Who is the histologist
Accordingly, a histologist or histopathologist is a physician 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, the scraping during the examination by a gynecologist, a small amount of tissue or fluid taken from a biopsy of tumor diseases. It can also examine sputum cells and various fluids from the pleura, effusion, or the abdominal fluid.
Histopathologists are responsible for making diagnoses after tissue examinations and this helps clinicians very much in treating patients. After all, they work closely with other clinical specialties, such as a gynecologist, oncologist, surgeon, neuropathologist and many others.
What skills should have
Doctors of this specialty should be attentive to detail for tissue research and diagnosis of diseases. 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, because the interpretation of what they see under the microscope will determine what kind of treatment the patient should receive.
Histopathologists must have a high degree of motivation and be able to work both independently and as part of a team. Good communication skills are necessary to discuss the relevance of microscopic data with fellow clinicians. Good diagnostic skills are very important to determine not only the type of disease, but also its severity and degree, which is necessary when choosing a treatment.
Why conduct a histological study
The method of histological diagnosis is actively used to determine the causes of infertility, diseases of the endocrine glands, inflammation of the internal organs, pre-tumor diseases. Another conduct is to identify the early stages of cancer in gastritis, ulcers, to establish the degree of liver damage.
Diagnosis of human organ biopsies 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 radicalism 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, neoplastic: malignant or benign);
- identify the disease before the patient complains.
This study is most often used to diagnose cancer. Indeed, without it, oncologists will not be able to carry out the correct treatment. Histologists treat cells and tissues removed from suspicious "lumps and cones", 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.
Currently, new methods are widely used in European countries, such as fluorescent in situ hybridization and polymerase chain reaction (PCR), to display genetic material in the tissues of tumors that are needed to treat many types of cancer.
Types of samples for detailed study
In the laboratory for the diagnosis of incoming materials that are taken at a puncture with a thin needle of a particular organ or neoplasm for research, also called puncture biopsy.
These are liquid or very small pieces of tissue, usually individual cells, rather than groups of cells, for example, a tumor in the lymph node.
Since the doctor can take only 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 tests can be endoscopy (for example, examination of the esophagus and stomach) or colposcopy (examination of the cervix with a magnifying instrument). An example of a more organized procedure is a kidney biopsy, when 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 with the naked eye, and key information is obtained only under a microscope. Many biopsies are encouraging because they were performed to rule out cancer. And it does not confirm cancer, but may, for example, show inflammation, which explains the clinical symptoms and signs in a patient. Other biopsies can show atypical cells and the histologist is already looking for signs that determine which cancer is present, how much the process is running and whether it will respond to certain types of treatment.
In addition, samples that are removed during surgery will be placed on the laboratory's table. It can be either a whole organ or a neoplasm, or a small area of them. Examples include the uterus after a hysterectomy, the colon after a colectomy, or the tonsils after tonsillectomy. A histopathologist carefully examines these samples with the naked eye and cuts off small pieces of tissue for examination under a microscope for more detailed examination. They require less surgical procedures, can be performed without anesthesia, sometimes using a soothing injection scraping the cervical canal from the uterus, 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 the successful treatment. This should be done in no more than 20 minutes.
The surgeon removes a small amount of tissue and waits until the histologist draws conclusions and makes a diagnosis before deciding how to proceed.
The patient sleeps under anesthesia while this is happening, and knows nothing about it. Quite often, doctors-histologists bring good news, for example, finding that a part of the test organ 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 following describes the process through which virtually all samples pass.
Step one - fixing the fabric. Slide preparation begins with fixing your sample. This is important in tissue preparation, and the purpose of this is to prevent tissue autolysis and decay. For best results, biological tissue samples should be recorded immediately after collection. Best of all this occurs in 10% neutral buffered formalin.
The optimal volume ratio of formalin to the 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 should be hermetically sealed and properly labeled.
Step two - transfer the material to the cassette. After fixation, samples are cut with a scalpel so that they can fit into the appropriate labeled tissue cassette. They should not be so large as to fill the whole cassette - they are cut so that they do not touch the edges. In addition, the materials studied should not be too thick (ideally they should be less than 4 mm), otherwise there is a risk of becoming a “waffle” when the cassette cover closes. The filled tissue cassettes are then stored in formalin prior to treatment.
Step three - tissue processing. It can last from four hours to thirteen hours depending on their size. Processing of tissues 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 the fabric. Paraffin wax replaces xylene and constantly penetrates the fabric. Then the plastic cassettes containing pieces of cloth are 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 over the form. After cooling, the upper part of the cassette and paraffin embedding fabrics become one unit, known as a 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 then passes through the blade. Each time a block passes a blade, it moves forward three or four micrometers. This is about the thickness of a single tissue cell.
When the fabric continues to pass through the blade, several sections of it are reproduced in a long tape. This tape is selected by a laboratory technician and floats in a bath of warm water. When all irregularities are smoothed, a histologist takes them out of the water. A slide with a very thin area of paraffin and tissue is the result of microtomy.
The fifth step is staining. Most cells are transparent and appear almost colorless when they are not stained. Two coloring agents 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 fabric outside the cell ranges from dark pink to red. This makes tissues more visible and easier to assess cellular composition.
It can be concluded that the histologist confirms or refutes various diseases in the human body that have been supplied by other clinicians. Without his final diagnosis, doctors cannot prescribe the correct and effective treatment. That is why the work of the histologist is very important and responsible for medicine today.