Pathology dictionary -
A biopsy is a type of surgical procedure where a doctor removes a small sample of tissue from your body and sends it to a pathologist for examination under the microscope.
Why is a biopsy performed?
A biopsy typically is performed on an area that appears abnormal. For example, a female patient with a 'lump' in her breast may undergo a biopsy of the lump in order to determine if the lump is non-cancerous or a cancer. Or a patient with stomach pain may undergo a stomach biopsy to see if the pathologist can see any condition or disease under the microscope that could explain the pain. In both cases only a very small piece of tissue is removed and sent for pathological examination.
The goal of a biopsy is to provide a diagnosis that can explain what is happening not just in the small sample of tissue, but in the entire area of interest (for example, provide a diagnosis for the entire 'lump').
Biopsies are performed to make a first diagnosis
Biopsies are often performed to provide a first diagnosis. This is particularly important when the diagnosis will determine the type of treatment you will receive. For example, if the biopsy performed on the patient with the 'lump' in their breast is diagnosed as a non-cancerous tumour (a benign tumour), the patient may undergo a small surgical surgery or no surgery at all. However, if the biopsy is diagnosed as a cancer (a malignant tumour) the patient will undergo a larger surgical procedure and may even receive chemotherapy.
Biopsies are performed to provide information about a known disease
Biopsies can also be performed to monitor the status of a known disease or to see if a treatment has been successful. For example, a patient with Crohn's disease will undergo biopsies at regular intervals to monitor the status of the disease. Alternatively, a patient with breast cancer may undergo a biopsy after receiving chemotherapy to see if there is any cancer left in the breast.
Limitations of a biopsy
Biopsies are not usually performed to remove an entire area of abnormal tissue or to cure a patient of a disease. For example, a biopsy performed on a patient with a 'lump' in their breast will usually not remove the entire lump. The biopsy is simply performed to provide a diagnosis. A more extensive surgical procedure, either an excision or a resection, would be performed to remove the entire lump.
Because a biopsy only provides information about the small piece of tissue sampled, it is always possible that some of the tissue not sampled contains important information that would change the diagnosis. For this reason, pathologists will only make a diagnosis based on what they can see in the sample of tissue provided to them.
In some cases this will mean that the pathologist will only provide a partial diagnosis. For example, a biopsy performed on a large mass in a patient's leg may be diagnosed as a cancer (a malignant tumour) without specifying the exact type of cancer present. When the entire tumour is removed, all of the tissue will be examined and a complete diagnosis will be provided.