biopsy

biopsy A piece of tissue taken from a patient during life to establish a precise diagnosis so that the most appropriate treatment can be initiated. Usually a thin section of the specimen on a glass slide is examined by a pathologist under a microscope, but if the specimen is small and soft it may be more appropriate to make a smear on the slide. On occasion the biopsy may require to be examined biochemically. Biopsies may also be taken, for example, from chorionic villi (the projections of fetal tissue around the early embryo after it is embedded in the womb) for chromosomal analysis when a hereditary disorder is suspected.

The technique of biopsy is vital in all branches of medicine. Various methods are used. The simplest is a scraping from an accessible site such as the skin, or from a mucous membrane, such as in the mouth or the cervix of the womb. One of the commonest is a needle biopsy when a small sample is sucked out into some type of syringe through a needle of a calibre appropriate to the consistency of the tissue. This method is applicable to obtaining tissue from the breast, kidney, liver, brain, or heart.

In other situations a lesion is biopsied by a surgeon either at an operation undertaken just for that purpose, or in the course of an exploratory procedure. Often only part of the lesion being investigated is taken at operation — an incisional biopsy, but if the lesion is small, such as an ulcer, a pigmented spot on the skin, or a lymph node it may be removed in its entirety: an excision biopsy. Procedures of this type involve the use of a scalpel. Other instruments may be appropriate: a curette is used to take scrapings from the inner lining of the womb (the endometrium); small biopsies may be obtained by endoscopy — from the lungs during bronchoscopy, or from the lining of the stomach or colon. Occasionally specially designed instruments are used, in the form of ‘punches’ or ‘brushes’.

One of the commonest reasons for undertaking a biopsy is to establish whether a tumour is malignant or benign. A common example of this is the investigation of a lump in a woman's breast. In such circumstances the pathologist often undertakes an immediate microscopical examination while the patient is still in the operating theatre, the surgeon waiting for the result before deciding how extensive an operation is required. This is also a common procedure during operations for tumours of the brain, or for cancers in other sites when lymph nodes need to be examined to establish whether or not they have been invaded by malignant cells.

Apart from the assessment of malignancy, biopsies are taken to examine organs such as the liver or kidneys for evidence of intrinsic disease, or to look for any signs of rejection of a transplanted organ such as a kidney or a heart.

Needle biopsies of skeletal muscles are often taken because of the problems frequently encountered in distinguishing clinically among conditions caused by disease in the muscle itself (myositis, muscular dystrophy) and those secondary to an abnormality in its nerve supply.

Healthy individuals are not always exempt — for example they may be recruited as volunteers for muscle biopsy. Enthusiasm for competitive sport and interest in the health-promoting effects of exercise in recent decades have provided an increasing incentive (and funds) for improving knowledge about skeletal muscle and the effects upon it of various training and dietary regimes. Needle biopsy of muscles has become a standard component of investigations in major research laboratories for sport and exercise science.

J. Hume Adams

See also cancer; muscle; neoplasm; transplantation.