Biopsy Health Article

Biopsy

A biopsy describes the procedure that is used to obtain a very small piece of the target tissue. For some tissues, like the lining of the cheek, cells can be obtained just by scrapping the tissue surface. Other samples are collected using forceps that are positioned at the end of an optical device called an endoscope. The physician can view the tissue surface (such as the wall of the large intestine) through the endoscope and use the forceps to pluck tissue from the desired region of the surface. In other cases, the tissue sample needs to be collected as a "plug," using a large hypodermic needle. Examples of the latter include liver or kidney biopsy samples. Samples of muscles and nerves can also be obtained by cutting out a small piece of the target once an incision has been made.

When a biopsy is obtained using a needle, the retrieval of a sample relies on the design of the needle and the energy of its insertion into the tissue. The needle used is a hollow tube with a sharp point capable of puncturing tissue. As the needle is driven deeper into a tissue following puncture, tissue will accumulate in the hollow tube. When the needle is withdrawn from the tissue, the plug of tissue remains in the needle tube and can be retrieved for analysis.

Many biopsy samples are examined using a light microscope to look for abnormalities in the tissues cells. This examination can involve the staining of the sample to specifically detect target molecules. As well, samples can be used for various biochemical tests, and even to test for the presence and activity of particular genes.

A biopsy can remove the entire target region (excisional biopsy) or can remove just a small portion of the target region (incisional biopsy). The latter can be done in three different ways, depending on the sample. A shave biopsy slices off surface tissue. Samples collected by piercing the tissue with a needle represent a punch biopsy. Finally, in fine needle aspiration, a needle is inserted and tissue is subsequently withdrawn into the needle using a syringe.

Definition

A biopsy is the removal of a small portion of tissue from the body for microscopic examination.

Description

When a physician diagnoses the nature of an ailment, various examinations provide information that is vital to accurately determining the nature of the problem. Blood and urine samples can be examined to determine the amounts of various compounds. As useful as this information can be, it reveals little about the state of tissues. In diseases such as cancer, knowledge of the affected tissue is crucial for diagnosis and the formulation of treatment strategies.

Examination of tissues can be accomplished without obtaining a sample, using techniques like ultrasound and magnetic resonance imaging (MRI). However, the information gained may not be detailed enough for a definitive diagnosis. For example, a physician may be interested in the activity of a particular enzyme in the tissue, as a marker of a disease process, or the presence of a toxin. For such determinations, a tissue sample that can be analyzed in the laboratory is needed.

Similarly, for certain diseases and conditions that involve nerve abnormalities, the ability to directly examine nerves can be advantageous in diagnosis and treatment. For instance, direct microscopic examination of a nerve sample can reveal whether or not the protective myelin sheath that surrounds a nerve is intact or is in the process of degrading. Obtaining a nerve via a biopsy is a valuable aid to these examinations.

Muscle biopsies can serve a similar purpose, since maladies that affect the structure and/or functioning of nerves will ultimately affect the muscles into which the nerve passes. The loss of muscle function or strength can be the direct consequence of nerve damage.

Muscle biopsy

A muscle biopsy can represent the punch type, in which a plug of tissue is obtained using an inserted needle. Or, in an open biopsy procedure, a small incision is made and a piece of tissue is removed. This biopsy is done for a variety of reasons: to distinguish between nerve and muscle disorders, to identify specific muscular disorders such as muscular dystrophy, to probe muscle metabolic activities, and to detect muscle infections such as trichinosis and toxoplasmosis. Biopsy of a muscle necessarily involves nerves, as muscle is highly infused by nerves. The small amount of muscle that is extracted during a muscle biopsy does not damage nerves to such an extent that muscle function is affected.