As early as the mid-17th century, the microscope, invented fifty years earlier, enabled natural scientists to conduct new research. Blood cells, sperm, and anatomical structures were discovered, and it began to be used to search for causes of disease. Many findings would be unthinkable even today without this tool.
Cells and tissues – basic substance of the body
Cells are the smallest units in the organism capable of living and reproducing. Bacteria have only one cell, whereas humans are composed of about 10,000 billion cells that are constantly renewed. Every second, several million perish in the human body and are newly formed. They are multiform and perform a wide variety of functions. In association with the intercellular substance, they form tissue that in principle fulfills four basic functions: Cover tissue (e.g., skin), connective and supporting tissue, muscle tissue, and nervous tissue.
Insights under the microscope
Cells and tissues obtained from the living can be viewed under a microscope. It is usually clear to see the location from which they originated. For example, biopsy material obtained from the liver looks different from that obtained from the mammary gland, and smears from the oral mucosa contain different cells than those from the cervix. But the pathologist is able to see even more. Since he knows exactly the healthy structures and their peculiarities, he notices even minor changes. For example, inflammations or diseases of the liver and kidneys produce typical signs. Microscopic examinations can also be used to detect pathogens and for functional diagnostics, e.g. in the case of hormonal disorders. It is no longer possible to imagine diagnostics without the fine-tissue evaluation, especially in the diagnosis of tumors. The various cancer cells are usually easy for the specialist to recognize and clearly differentiate. They allow statements to be made about the type of tumor and its spread. Staining techniques and coupling with labeled antibodies can distinguish cell types even more precisely.
How are cell and tissue samples obtained?
- In principle, a distinction is made between smears and biopsies.For a smear, cell material or secretion is obtained from the surface, using a brush, cotton swab or spatula. A typical example is the smear from the vagina and cervix as part of the gynecological screening examination. The advantage of a smear is that with him no tissue damage occurs and no side effects are expected.
- In a biopsy, on the other hand, a tissue sample is also obtained from deeper layers by means of pricking, punching, suction, cutting or scraping with various tools such as hollow needles or scalpel. The advantage compared to the smear is that this allows access to other parts of the body, provides more accurate information about deeper layers, and preserves 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 also from the right place and not to injure other structures.
What is examined and how?
- Swabs can be taken from skin and mucous membranes (e.g., nose, mouth, vagina, intestines) and are used to detect disease and inflammation as well as cancer cells or their precursors. The collected material is spread on a glass slide, fixed and usually stained. Sometimes it is also viewed unprocessed under a microscope. Pathogens can also be detected in the smear, e.g. in the secretion of chronic wounds. For this purpose, the material is cultured on suitable nutrient medium. Most often, smears are taken from wounds (eg in diabetics), the throat (if a purulent sore throat is suspected), vagina (suspected infection), cervix (cancer screening) and eye (of cornea and conjunctiva if infection is suspected).
- Biopsies tend to be used at the end of a diagnostic chain, when not all questions have been answered despite other tests such as blood tests, ultrasound, X-rays and computed tomography. Biopsies can be taken from almost any organ or tissue. Tissue from the breast, prostate, thyroid, intestine, and bone is especially commonly obtained when cancer is suspected. Liver, kidney, and heart are primarily punctured for inflammation. A muscle or nerve biopsy is used to diagnose muscle, nerve and metabolic diseases. As part of prenatal diagnostics, a sample can also be obtained from the villous membrane 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 been successfully accepted and grown in. The tissue removed during a biopsy is often cut into fine slices and stained. Sometimes it is additionally marked with special antibodies.
The preparation and execution
No special preparation is required for a smear test. The doctor gently takes the material from the appropriate place with a cotton swab or flat spatula and sends it – in special packaging – quickly to the laboratory. In the case of a biopsy, the preparation depends on the site from which the material is obtained. For biopsies in the abdomen, the patient should be fasting; it may be necessary to shave the puncture site. Biopsy is a minor procedure involving tissue injury, so it must be performed under sterile conditions. This means that the physician wears sterile gloves, the puncture site is carefully disinfected and the instruments are sterile. Whether the procedure is painful also depends on the sampling site. In most cases, the biopsy is performed under local anesthesia; in addition, the person may be given a painkiller and sedative beforehand. Often, the tissue is taken by puncture with a hollow needle that is pierced through the skin. A thin needle is called a fine-needle biopsy, while a thick needle is called a punch biopsy. The former is used, for example, in liver puncture, the latter in prostate puncture. If the target is far inside, imaging is often used to assist and monitor. Sometimes larger, contiguous areas are excised with a scalpel, allowing direct therapy if necessary. This excisional biopsy is mainly used for skin tumors. Another possibility is the removal of tissue during an endoscopy. In this way, material can be obtained from body cavities such as the stomach, intestines or lungs. In this case, small instruments such as forceps, brushes, or punches are inserted into the endoscope and the biopsies are taken under visual control.
Are there risks?
There are no risks associated with a pap smear. Because a biopsy involves tissue injury, it carries certain risks, as does any procedure. However, these can be minimized by careful, germ-free work by the physician. Germs can enter the body during a puncture and cause an infection. The needle can accidentally injure other structures and cause bleeding. The risk of carrying cancer cells with the biopsy needle is now considered very low. The risks in detail vary depending on the biopsy, but are explained in detail to the individual by the attending physician before the procedure.
