Stereotactic Needle Biopsy
Stereotactic needle biopsy (SNB) is an ultrasound-guided and mammogram-directed needle aspiration biopsy of breast tissue. It is a diagnostic procedure used
Stereotactic needle biopsy is performed when non-palpable (unable to be felt) abnormalities are identified by mammogram. The abnormality is generally located on a routine screening mammogram. This biopsy procedure uses a large (core) or small (fine) needle that withdraws samples of the abnormal breast tissue. The doctor uses either the mammogram or an ultrasound image of the abnormal tissue to guide the needle to the biopsy site. The needle is used to remove tissue samples of the site for laboratory analysis.
The patient is made comfortable with a local anesthesia injection prior to the start of the procedure. Special imaging techniques are used to localize (easily see) the abnormal spot. First, the patient lies face down on a table with breasts suspended through an opening. Then mammograms are taken of the suspicious site from several different angles. This technique creates a virtual three-dimensional (stereotactic) picture of the abnormal area. A computer is used to guide the needle to the site for sample removal. If the abnormality can be seen easily on ultrasound, the biopsy may be performed with the patient lying on her back while ultrasound imaging localizes the abnormality. The samples are examined in the laboratory by a pathologist (a physician trained in identification of pathological or abnormal findings) to determine if cancer cells are present.
There are two different types of needles used for stereotactic needle biopsy. The procedures are similar, but the size of the needle varies. A fine-needle biopsy is most often used, in conjunction with ultrasound imaging, when a cyst is suspected. The doctor is able to suction a sample of fluid or tissue through the needle and send it for analysis. The needle is smaller and so is the sample of fluid or tissue extracted. In a core needle biopsy, the needle is larger, has a cutting edge, and enables the physician to extract a larger tissue sample from the suspicious area. A larger tissue sample can enhance laboratory accuracy in identifying the presence of cancer cells.
Prior to ordering a breast biopsy, the physician gathers as much information from the patient as possible by asking questions that provide a medical history. The physician will perform a clinical breast examination through palpation to determine any changes from previous exams or to determine a baseline exam. The physician orders a routine screening mammogram (x ray) and interprets the results. If something abnormal is revealed on mammogram, further radiologic exams are requested. After confirming the presence of a radiographic abnormality, the physician will order a biopsy. A patient's written informed consent is necessary before any invasive procedure. The document should explain, in understandable language, the patient's treatment options, risks and benefits of the procedure, and potential complications.
General anesthesia is not used for the stereotactic needle biopsy procedure. Usually the physician will use a local injectable anesthetic agent at the needle insertion site to numb the area. When the anesthetic is injected at the biopsy site, the patient will feel a stinging sensation. The physician will wait until the numbing agent takes effect, then proceed with the biopsy. At this point, the patient should only feel a pressure sensation as the needle is guided to the biopsy site.
Patients should discuss the indications (reasons for) and contraindications (reasons why not) of having a stereotactic needle biopsy performed with their doctor. While the procedure has been studied extensively with positive outcomes for accuracy of results, it is most indicated in cases where there is a non-palpable area of abnormal tissue identified by mammogram. However, vaguely palpable abnormalities can also be managed in this way. Physicians divide "abnormal findings" into several categories. A probable benign finding is a category 3, a suspicious abnormal finding is a category 4, and a highly suggestive of malignancy finding is a category 5.
When there is a probable benign finding (category 3), frequently there is no previous mammogram for comparison study. A stereotactic needle biopsy is done on a category 3 finding when there is a strong family history of breast cancer. Usually, a category 3 finding requires only a six month follow-up with mammography.
When there is a suspicious abnormality (category 4), a sterotactic needle biopsy is most useful, as well as indicated. In this category, stereotactic needle biopsy is used to differentiate those patients requiring surgical intervention from those needing clinical and mammographic (xray) follow-up.
In a category 5 finding, highly suggestive of malignancy, the physician can use information from a stereo-tactic needle biopsy to confirm a diagnosis and expedite surgical intervention in this category.
Stereotactic needle biopsy is not indicated in all cases where there is nonpalpable breast tissue abnormality.
After the procedure, the patient may experience pain or discomfort at the biopsy site. Mild bruising can also occur at the site. For these reasons, the physician may suggest that activities be limited for 24 to 48 hours post-procedure. The physician will suggest or prescribe a medication for discomfort relief. Often, a sport bra or other firm support garment will minimize breast movement and increase post-procedure comfort. Icing the area may also be reccommended. The physician will inform the patient of further follow-up care needed to monitor the patient's ongoing breast health and the subsequent intervals for follow-up imaging.
It is very important for the patient who is facing a stereotactic needle biopsy procedure to know that there is the possibility of needing a repeat biopsy procedure. A repeat biopsy is necessary if there is a discrepancy between the radiology reports and the pathologist's findings from laboratory analysis of the sample (concor-dance). As with any procedure, there is a slight risk of allergic reaction to anesthesia. To be well informed, patients should consult with their physician about the risks prior to undergoing SNB.
Stereotactic needle biopsy is a diagnostic tool used to determine the presence of cancer cells. It is not a therapy used to obliterate an area of abnormal tissue. The results of the biopsy help the physician to determine the best medical or surgical options available to the patient. The biopsy results are reviewed by the physician performing the SNB and by the pathologist who analizes the sample. Results are reviewed and discussed with the patient and options for further treatment or follow up are presented. The patient, with the guidance and expertise of the physician, selects a course of therapy.
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Molly Metzler, R.N., B.S.N.