Stereotactic biopsy uses specialized mammography equipment to calculate precisely the location of a lesion in three dimensions. Stereotactic biopsy can be performed with the patient prone on a dedicated table or with the patient sitting in an upright unit. Digital equipment is available for stereotactic biopsy, which dramatically decreases the amount of time necessary to perform the procedure. Stereotactic biopsy can be used for all types of mammographic lesions (i.e., masses and calcifications).
To perform stereotactic biopsy on a dedicated table, the patient is positioned prone and the lesion is localized with a scout image. Two mammographic images are obtained (usually at 15° oblique angles from the scout film). The same point is identified on both views and communicated to the computer, usually by means of a hand-held mouse or cursor, allowing the computer to calculate the coordinates of the lesion in three dimensions.
The skin is cleansed with iodinated soap and anesthetized with local anesthesia.
A skin nick is made with a scalpel, the tissue acquisition device (e.g., automated core needle or directional vacuum-assisted biopsy probe) is inserted, and its positioning confirmed on two angled stereotactic images. Multiple tissue specimens are obtained and sent in formalin for pathologic analysis.
Ultrasound can be used to guide biopsy of mass lesions that can be identified with ultrasound examination. Advantages of ultrasound include the multipurpose use of the equipment, lack of ionizing radiation, the lack of breast compression during the procedure, accessibility of all areas of the breast and axilla, multidirectional sampling and ability to observe the needle in real time.
To perform ultrasound-guided 14-gauge automated biopsy, the patient is positioned in the supine oblique position, the area is localized with real-time sonography and anesthetized with lidocaine, and a skin nick is made with a scalpel. The 14-gauge automated needle is inserted and its accurate position confirmed with real-time imaging. Multiple samples are obtained and sent for pathologic analysis.
Previous studies have reported excellent results with ultrasound-guided 14-gauge automated core biopsy. Parker et al reported 100% concordance between results of ultrasound-guided 14-gauge automated core biopsy and surgery in 49 lesions that went to surgery, and no carcinomas at 12 to 36 month follow-up in 132 lesions for which ultrasound-guided core biopsy yielded benign results.
Liberman et al found that ultrasound-guided core biopsy obviated a surgical procedure in 128 (85%) of 151 lesions, resulting in a decrease in the cost of diagnosis by 56%. In that study, the investigators found that both ultrasound-guided core biopsy and stereotactic core biopsy were less expensive than surgery, but cost savings were higher if the biopsy was performed under ultrasound guidance.