Since the middle of the 17th century, the fifty-year-old microscope made new research possible for scientists. Blood cells, sperm, and anatomical structures were discovered, and disease scans began. Many findings would be unthinkable even today without this tool.
Cells and tissues - basic substance of the body
Cells are the smallest living and reproducible units in the organism. Bacteria have only one cell, whereas humans are composed of about 10, 000 billion cells, which are constantly renewed. Every second, millions of people die in the human body and are newly formed. They are multifarious and perform different functions. In association with the intercellular substance, they form tissue that basically fulfills four basic functions: covering tissue (eg skin), connective and supporting tissue, muscle tissue and nerve tissue.
Insights under the microscope
Cells and tissues obtained from the living can be viewed under the microscope. As a rule, it is clear to see from where they come from. Thus, biopsy material obtained from the liver looks different from that from the mammary gland and smears from the oral mucosa contain other cells than those from the cervix. But the pathologist is able to see more. Because he knows exactly the healthy structures and their idiosyncrasies, he also notices minor changes. For example, inflammation or diseases of the liver and kidney cause typical signs.
Also for pathogen detection and functional diagnostics, eg for hormonal disorders microscopic examinations can serve. It is no longer indispensable to perform a histological assessment, especially in the diagnosis of tumors. The various cancer cells are usually easy to recognize for the expert and clearly differentiate. They allow statements about type of ulcer and its spread. With staining techniques and the coupling to labeled antibodies, the cell types can be distinguished even more accurately.
How are the cell and tissue samples obtained?
- In principle, a distinction is made between smears and biopsies. For a smear, cell material or secretions are collected on the surface using brush, cotton wool or spatula. A typical example is the vagina and cervix smear as part of the gynecological check-up. The advantage of a smear is that it does not cause any tissue injury and no side effects are to be expected.
- In a biopsy, on the other hand, a tissue sample is also obtained from deeper layers by means of piercing, punching, sucking, cutting or scraping with various aids such as hollow needles or scalpel. The advantage over the smear test is that it makes it possible to access other parts of the body, to obtain more accurate information about deeper layers, and to preserve the cells in the dressing. The biopsy is often performed under ultrasound or X-ray control - so the doctor is sure to take the sample from the right place and not to injure other structures.
What is being investigated and how?
- Swabs can be taken from the skin and mucous membranes (eg nose, mouth, vagina, intestine) and are used to detect diseases and inflammations as well as cancer cells or their precursors. The removed material is spread on a glass slide, fixed and usually dyed. Sometimes it is also viewed unprocessed under the microscope. In the swab also pathogens can be detected, for example in the secretion of chronic wounds. For this purpose, the material is grown on suitable nutrient medium. Smears from wounds (eg in diabetics), the throat (in suspected purulent throat infection), vagina (suspected infection), cervix (cancer prevention) and eye (from the cornea and conjunctiva in suspected infection) are most often taken.
- Biopsies are more likely to be used at the end of a diagnostic chain if, despite other tests such as blood tests, ultrasound, X-rays and computed tomography, not all questions have been resolved. Biopsies can be taken from almost every organ and tissue. In cases of suspected cancer, tissue from the breast, prostate, thyroid, intestine and bone is most frequently obtained. Liver, kidney and heart are punctured especially in inflammation. A muscle or nerve biopsy is used to diagnose muscle, nerve and metabolic diseases. In prenatal diagnosis, a sample can also be obtained from the skin of the villi surrounding the unborn child. Some biopsies are also suitable for the follow-up of therapies - after an organ transplant, for example, it is possible to assess whether the new tissue has successfully acquired and grown. The tissue removed during a biopsy is often cut into thin slices and dyed. Sometimes it is additionally labeled with special antibodies.
The preparation and execution
For a smear, no special preparation is required. The doctor gently removes the material at the appropriate place with a cotton swab or flat spatula and - in special packaging - sends it quickly to the laboratory. In a biopsy, the preparation depends on the location from which the material is obtained. In biopsies in the abdomen of the affected person should be sober; maybe a shave at the puncture site is necessary. Biopsy is a minor procedure involving tissue injury, so it must be performed under sterile conditions. This means that the doctor wears sterile gloves, the puncture site is thoroughly disinfected and the instruments are germ-free.
Whether the procedure is painful also depends on the donor site. Mostly the biopsy is done under local anesthesia; In addition, the person concerned can previously receive a painkiller and sedative. Often the tissue is removed by puncture with a hollow needle, which is pierced through the skin. A thin needle is called fine-needle biopsy, and a thick one is punch biopsy. The former is used eg in liver puncture, the latter in the prostate function. If the target is located far inside, an imaging process is often used to assist and control. Sometimes larger, contiguous areas are cut out with a scalpel and, if necessary, therapy is performed directly.
This excisional biopsy is mainly used in skin tumors. Another possibility is tissue removal during a reflection. This allows material to be extracted from body cavities such as the stomach, intestines or lungs. Small instruments such as forceps, brushes or punches are inserted into the endoscope and the biopsies are removed under view.
Are there risks?
A smear is without risks. Because a biopsy is associated with a tissue injury, it carries - as any intervention - certain risks. However, these can be minimized by careful, germ-free work by the doctor. In a puncture, germs can enter the body and cause an infection. The needle can accidentally injure other structures and lead to bleeding. The risk of carrying cancer cells with the biopsy needle is now considered to be very low. The individual risks vary according to the biopsy, but are explained to the patient in detail before the intervention by the treating physician.