Why and when a biopsy is necessary
What is a biopsy?
According to the definition provided by the National Cancer Institute, a biopsy (by-op-see) is the removal of cells or tissues (from a growth, organ, or lesion) for examination by a pathologist. The pathologist may study the tissue under a microscope or perform other tests on the cells or tissue.
What are the types of biopsies?
There are several different types of biopsies that can be performed: an incisional biopsy is when only a sample of tissue is removed. An excisional biopsy is when an entire lump or suspicious area is removed. A needle biopsy, core biopsy, or fine-needle aspirate is when a sample of tissue or fluid is removed with a needle. Any of these types of samples may provide the pathologist with sufficient information to make a diagnosis of cancer. However, the rule ‘more is better’ generally applies when it is important to accurately classify and stage that cancer.
Why is a biopsy needed?
Non-invasive tests such as radiographs, ultrasound, or magnetic resonance imaging (MRI) can indicate suspected cancer, but a biopsy provides the tissues needed to make a definitive diagnosis.
What is a fine needle aspirate (FNA) and what are the pros and cons?
A fine needle aspirate is a first-line procedure which can narrow the list of possible diagnoses. In many cases, it provides all the information needed to formulate a treatment or management plan. The FNA is the least invasive biopsy procedure. The patient is usually awake or only lightly sedated, a needle is inserted into the abnormal tissue, and cells are pulled (aspirated) into the needle and the syringe. The cells can then be placed on a glass slide for microscopic examination (cytopathology), or they can be placed in a preservative for other tests. The advantages of the procedure are that it is minimally invasive and generally very safe, it is less costly than an incisional or an excisional biopsy, and the results can be obtained rapidly. The disadvantages are that the tissue architecture is destroyed, so the information that can be learned from the sample is limited. Finally, the amount of sample is small, so additional tests require additional samples.
What is an incisional biopsy and what are the pros and cons?
Incisional biopsies are more invasive than fine needle aspirates but can be obtained safely and at reasonable cost. A “tru-cut” biopsy tool, which is similar to a needle with a larger channel, is inserted into the tissue, and as it penetrates, it also cuts, allowing a small core to remain in the needle channel. This core of tissue is then removed and can be used for cell pathology, and it can be placed in a preservative for additional tests. The most common test done by a pathologist is examination of formalin-fixed and paraffin embedded tissue that has been subjected to several additional processing and staining steps under the microscope. The advantages of an incisional biopsy are that there is more tissue available for analysis, and the architecture, or the context of how cells relate to each other, is preserved. In addition, the preserved tissue allows the pathologist to perform additional tests without the need to obtain additional samples. This provides a more complete picture to accurately classify and stage the disease. Because tissue imprints can be obtained from these samples, a provisional diagnosis can also be obtained. The disadvantages are that it is more invasive (it usually requires at least a small “nick” in the skin to allow the needle to be placed into the tissue), it requires heavy sedation or general anesthesia, it takes longer to process and read, and consequently, it is more costly. In some cases, it is necessary to remove a large piece of tissue (“wedge biopsy”) in order to provide the pathologist sufficient material to reach a diagnosis.
What is an excisional biopsy and what are the pros and cons?
Excisional biopsies are done when there is an opportunity to remove the whole tumor without significantly added risk to the patient. The advantages and disadvantages are like the incisional biopsy above. An example of an excisional biopsy is removal of a lymph node.