A biopsy is the removal and microscopic examination of tissue from a living patient for purposes of diagnosis. The tissue is removed by needle, suction, swabbing, scraping, or excision. Most biopsies are minor procedures that require no sedation, but some require local or general anesthesia.
Biopsy is an accurate method of diagnosing many illnesses, including cancer. The term biopsy is also commonly used for the cell or tissue sample itself (although the term biopsy specimen is more correct).
Why biopsy is done
Microscopic examination of tissue (histology) or of cells (cytology) usually gives a correct diagnosis. Biopsy is valuable for discovering whether a tumor is benign or malignant, since a malignant tumor usually has many features that clearly distinguish it from a benign tumor. In the case of a malignant tumor, biopsies of the surrounding tissue and the lymph nodes can be done to determine whether the cancer has spread. Another important use of biopsies is to determine the cause of unexplained infections and inflammations.
How biopsy is done
This consists of cutting away a small piece of skin or muscle for analysis. Usually a local anesthetic is required.
A needle is inserted through the skin and into the organ or tumor to be investigated. The needle may be fitted with a cutting tip to help remove a piece of tissue for examination. Aspiration biopsy is another type of needle biopsy in which the cells that are sucked from a tumor are examined cytologically. Usually, only a local anesthetic is required.
Until recently, if the target area could not be felt through the skin, or the organ was not accessible by endoscopic biopsy (see below), the doctor would have to work blindly, relying only on experience and a knowledge of anatomy, so that deep-needle biopsy was almost never done. Today, guided biopsy, using ultrasound scanning or CT scanning to precisely locate the tissue to be biopsied and follow the progress of the needle, makes the procedure far more accurate, safe, and productive. In addition, the recent use of very fine needles for biopsies allows for safe sampling of tumors in organs such as the salivary glands and pancreas, in which sampling with larger needles was considered dangerous.
An endoscope is passed into the organ to be investigated and an attachment (such as forceps to remove tissue or brushes to remove cells) is used to take a sample.
This is part of an operation, usually requiring general anesthesia, in which the surgeon opens a body cavity, such as the chest or abdomen, to reveal a diseased organ, or tumor, and removes a sample of tissue. Open biopsy is carried out when neither guided nor endoscopic biopsy is possible, or when it is likely that the organ or tumor will require removal. Prompt analysis of a tissue sample can enable the surgeon to decide whether to remove the entire diseased area immediately, so making a second operation unnecessary.
If a lump is found in the skin or an organ, such as the breast, the surgeon may remove the lump completely and send the whole specimen for laboratory examination. If an abnormality is detectable only by an imaging technique, such as mammography, injected dye or fine wire probes may be used to identify the abnormal area for the surgeon.
Obtaining a result from biopsy
When immediate diagnosis is essential (e.g., to enable breast cancer to be operated on without delay), the biopsy sample is prepared for preliminary microscopic examination in a few minutes by freezing or by smearing cells on to slides.
The sample may also be prepared for later, more detailed examination. For a tissue sample, this usually involves embedding the sample in wax and then staining it with dyes to show up structures more clearly or to identify particular constituents, such as antibodies or enzymes. In special cases, a biopsy sample may be examined under an electron microscope – for example, to determine the origin of certain tumors.
In the investigation of infections and inflammations, a tissue sample may be tested with specific antibodies. In some cases, a tissue culture may be required.
Many of the more specialized techniques for preparing biopsy specimens prolong the time required to make an exact diagnosis but allow for greater accuracy and more precise information about the outlook for patients with certain diseases.