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STEREOTACTIC BREAST BIOPSY
STEREOTACTIC IMAGE GUIDED BREAST BIOPSY
When a breast lesion is not palpable but detected on a mammogram and diagnosed to be suspicious for malignancy, the lesion must first be localized using image guidance and a biopsy must be performed for tissue diagnosis.
Traditionally, the lesion undergoes needle localization by a radiologist followed by open excisional biopsy under general anesthesia by a surgeon in the operating room. In recent years, less invasive techniques have been developed and are being used more frequently. One of the new techniques is stereotactic breast biopsy.
The breast is compressed just as in regular mammography, except the compression paddle has a window. The x-ray tube can be positioned perpendicular to the image detector as well as +15 degrees and 15 degrees to the perpendicular. Localization of a specific lesion within a breast, by x-ray imaging, is based on measurements of the position of the lesion on two images of the breast taken from different angles (+15 degrees and 15 degrees). Such a set of images is referred to as a stereo pair. The radiologist selects the center of the lesion, a mass or specific calcifications of a cluster. A computer generates the X, Y and Z coordinates of the targeted lesion. The Z coordinate is the depth of the lesion from the skin. Some stereotactic units are upright with the patient sitting during the procedure. Other units include a table where the patient can lie prone with the breast hanging from a hole in the table. The prone table is more comfortable for the patient and decreases the possibility of motion.
Once the stereo pair is obtained and the exact location of the lesion is calculated, any of several devices may be employed to obtain tissue sample. The devices differ in the size of the tissue samples obtained the mechanism of obtaining the samples and whether the tissue sampling is noncontiguous, contiguous or possibly complete removal of the lesion. These devices include 1) a spring loaded core biopsy needle (14G), 2) a vacuum-assisted core biopsy device (Mammotome 14G or 11G and MIBB 8G) and 3) a larger core device (ABBI, 5mm, 10mm, 15mm, and 20mm). Local anesthesia is used with these devices and a skin incision is made to accommodate the device to be used.
Each of the above stereotactic core biopsy procedures can be performed on an outpatient basis under local anesthesia with the patient able to leave within an hour after completion of the biopsy. The localization and biopsy of the lesion are more accurate since there is direct visualization of the lesion during the procedure. This allows for directional adjustment if necessary. The procedures are less invasive and less disfiguring than open excisional biopsy and yield equal diagnostic accuracy. Since up to 80% of breast biopsies are benign, stereotactic breast core biopsy is an attractive alternative to open excisional biopsy for early diagnosis of breast cancer.
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