A biopsy is a diagnostic test involving the removal of small amounts of tissue or cells from the body for microscopic examination. A biopsy is an accurate method of diagnosing many illnesses, including cancer.
Microscopic examination of tissue (histology) or of cells (cytology) usually gives a correct diagnosis.
How it is done
There are several types of biopsy. In excisional biopsy, the whole abnormal area is removed for study. Incisional biopsy involves cutting away a small sample of skin or muscle for analysis.
In a needle biopsy, a needle is inserted through the skin and into the organ or tumour to be investigated.
Aspiration biopsy uses a needle and syringe to remove cells from a lump. Aspiration biopsy involves the following 3 steps:
- A fine needle attached to a syringe is inserted into the lump, and fluid or cells are sucked out to be examined under a microscope. The syringe can be held in a device that withdraws the plunger. Usually no anaesthetic is necessary, but local anaesthetic may be sometimes be used.
- Before examination any fluid may be spun at high speed in a centrifuge and a small amount placed on a slide.
- The cells are then fixed (preserved) and finally stained for viewing. The cytologist examines individual cells for abnormalities, paying particular attention to the size, shape, and structure of the nucleus.
Guided biopsy uses ultrasound scanning or CT scanning to locate the area of tissue to be biopsied and follow the progress of the needle.
In endoscopic biopsy, an endoscope (viewing tube) is passed into the organ to be investigated and an attachment is used to take a sample from the lining of accessible hollow structures such as the lungs, stomach, and bladder.
In an open biopsy, a surgeon opens a body cavity to reveal a diseased organ or tumour and removes a sample.
Prompt analysis, in some cases by frozen section (in which the tissue is frozen and thinly sliced), can enable the surgeon to decide whether to remove the entire diseased area immediately.
Obtaining biopsy results
Biopsy samples are analysed by staining; dyes are used to show up structures or identify constituents such as antibodies or enzymes. Tissue may be tested with specific antibodies in the investigation of infection and inflammation. In some cases, a tissue culture (cultivation of tissue cells in a growing medium) may be required.