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12 radiology.rsna.org n Radiology: Volume 268: Number 1—July 2013

1 From the Department of Radiology, Breast Imaging Center, University of Cincinnati Medical Center, 234 Goodman St, ML 772, Cincinnati, OH 45267 (M.C.M.); and Department of Radiology, Section of Breast Imaging, Emory University, Atlanta, Ga (M.S.N.). Received May 23, 2012; revision requested July 7; revision received October 5; accepted and final version accepted October 14. Address correspondence to M.C.M. (e-mail: mary.mahoney @uchealth.com).

q RSNA, 2013

Mary C. Mahoney, MD Mary S. Newell, MD

Breast Intervention: How I Do It1

Breast imaging has undergone many changes since the early years of mammography. Screening mammography is credited with contributing to the substantial decrease in breast cancer mortality through early detection. Screen-ing mammography programs allow depiction of nonpal-pable, suspicious findings requiring histologic evaluation, but most of which eventually are proved benign. Wide-spread acceptance of percutaneous breast biopsy tech-niques represents the most important practice-changing development in breast imaging. The radiologist now plays a vital role not only in the detection and evaluation of breast disease, but also in the diagnosis and management of breast cancer. Descriptions of the advantages of percu-taneous breast biopsy and the techniques of performing breast intervention are the focus of this review.

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HOW I DO IT: Breast Intervention Mahoney and Newell

Radiology: Volume 268: Number 1—July 2013 n radiology.rsna.org 13

The development and widespread use of percutaneous image-guided breast biopsies has expanded the

role of breast imaging and changed the management of breast disease. Valida-tion of the safety, accuracy, and cost- effectiveness of these biopsies has led to their replacement of the surgical biopsy for most breast lesions requiring a tissue diagnosis (1–17). The advantages of the minimally invasive core-needle biopsy (CNB) over surgical biopsy include less scarring, fewer complications, lower cost, and faster recovery. The success of a breast CNB program depends on both the performance of the procedure and the appropriate postbiopsy manage-ment. In this article, we outline a general approach to the image-guided percutane-ous breast biopsy and discuss specifics of the various acquisition devices and imag-ing modalities used for guidance.

Validation of Percutaneous Image-guided Biopsy

Approximately 70%–90% of the 1.6 mil-lion breast biopsies performed annually in the United States are image-guided

Published online 10.1148/radiol.13120985 Content codes:

Radiology 2013; 268:12–24

Abbreviations:CNB = core-needle biopsyVAD = vacuum-assisted device

Conflicts of interest are listed at the end of this article.

Essentials

n The development and widespread use of percutaneous image-guided breast biopsies has ex-panded the role of breast im-aging and changed the management of breast disease; image-guided percutaneous bi-opsies have replaced surgical bi-opsies for most breast lesions requiring a tissue diagnosis.

n Success of a percutaneous core-needle breast biopsy program requires meticulous technique and careful radiologic-pathologic correlation.

n Stereotactic, US-guided, and MR-guided biopsies are all validated, effective methods of performing percutaneous breast biopsy.

n US-guided biopsy is the preferred method of biopsy due to the ad-vantages of real-time imaging, greater patient comfort, lack of ionizing radiation, and lower cost.

percutaneous procedures (18,19). Ma-jority (approximately 80%) of the results will be benign (4). Confidence in benign, concordant image-guided CNB findings allows avoidance of unnecessary surgery. In 1994, using long-throw spring-loaded 14-gauge needles, Parker and colleagues showed an overall 1.5% false-negative rate for percutaneous breast biopsy (4). Other authors have confirmed the accu-racy of CNB, demonstrating excellent histologic agreement between CNB and excised specimens (5,13,20). In fact, sev-eral studies have demonstrated a lower “miss” rate for CNB (1.6%), compared with surgery (2.5%) with larger gauge needles and vacuum assistance (15,16). Nonetheless, sampling error can lead to histologic underestimates. Careful re-view of the pathology results, with rec-ommendation for excision of lesions known to be subject to upgrade (eg, atypical ductal hyperplasia), is necessary. Discordance between imaging and pa-thology results also requires excisional biopsy (21–24).

The safety of image-guided breast bi-opsy has been well demonstrated. Some centers prefer to stop administering blood-thinning agents prior to biopsy. Patients are instructed to discontinue as-pirin and nonsteroidal anti-inflammatory agents 1 week prior to biopsy. Coumadin is discontinued 3 days prior to biopsy, and an international normalized ratio level of less than 1.4 is confirmed the day of the biopsy. However, other centers proceed with biopsy without altering the patient’s anticoagulation regimen, as there is some evidence to suggest this is a safe practice (25). Parker and col-leagues (4) showed a 0.2% incidence (six of 3765 cases) of clinically important complications with use of large-core (14-gauge) needles. Similar results have been found with vacuum-assisted biopsy devices and larger (7–11-gauge) needles (13).

The cost-effectiveness of percutane-ous breast biopsy is due, in large part, to the ability to avoid surgery if benign, concordant results are obtained (8–10,13,15). However, cost savings are also realized when CNB findings show malig-nant results. A patient whose cancer is diagnosed with percutaneous biopsy can

expect to undergo fewer surgeries than a patient whose cancer is diagnosed with open surgical biopsy (1.25 vs 2.01) (17). Preoperative verification of malignancy allows definitive surgical therapy in one setting.

Current Procedures

The decision to perform an image-guided biopsy includes selection of the imaging modality to guide the biopsy and the type of biopsy device to be used. Stereotaxis, ultrasonography (US), and magnetic res-onance (MR) imaging are most fre-quently used for biopsy guidance. Newer aging modalities that use nuclear meta-bolic agents such as flu orodeoxyglucose and sestambi have necessitated the de-velopment of biopsy methods for these modalities, though they are infrequently used at this time (26,27). In general, the modality used for imaging guidance should be the one that best demonstrates the lesion. On the other hand, because of the numerous advantages of US guid-ance, attempts are made to identify US correlates to most lesions warranting bi-opsy (28,29). Particularly in the case of lesions identified at MR imaging and metabolic imaging, identification of a US correlate greatly simplifies the biopsy procedure. Ensuring that targets are concordant between the imaging tech-niques requires expertise and experience in imaging to translate expected lesion appearances and positions from one mo-dality to another.

Most image-guided biopsies are per-formed with either a spring-loaded or vacuum-assisted device (VAD). Fine-nee-dle aspiration is seldom used for evalua-tion of breast lesions. Acquisition of cyto-logic material with a fine-needle aspiration technique rather than acquisi-tion of histologic material with a large-



core needle is associated with a high rate of insufficient samples, higher false-nega-tive rates, inability to differentiate be-tween invasive and noninvasive cancers, and lack of sufficient tissue to define tu-mor biomarker status (30,31).

Preprocedural ConsiderationsWritten informed consent is required before all breast interventions. The risks explained to the patient include bleeding and infection. Anticoagulation is a rela-tive contraindication to all biopsies, and patients are usually asked to discontinue therapy for a short time prior to the bi-opsy. Local anesthetics are usually ade-quate for addressing the pain related to these procedures. Lidocaine 1% is fre-quently used. Superficial anesthetic buff-ered with sodium bicarbonate (bicar-bonate-to-lidocaine ratio of 1:9) decreases the burning sensation related to initial skin and subcutaneous injec-tion. Deeper anesthetic does not require buffering, but is usually administered with epinephrine (1:100 000) to prolong the anesthetic effect and to aid in hemo-stasis. The patient should be informed of the potential benefits of the biopsy, including avoidance of surgery with be-nign results or preoperative confirma-tion of malignancy, which allows defini-tive surgical treatment in one surgical setting.

An additional potential complication of US-guided biopsy is pneumothorax. However, with proper technique, this is an exceedingly rare complication (32). A few contraindications to MR-guided bi-opsy exist. Patients with implanted me-tallic or electronic devices and those with an allergy or renal risk factors re-lated to the contrast material cannot un-dergo MR imaging or biopsy. Presum-ably, the patient has already safely undergone a diagnostic breast MR imag-ing, but screening for any contraindica-tions to MR imaging should still be per-formed prior to the biopsy procedure. Claustrophobia is another relative con-traindication that is specific to MR imag-ing but can be problematic. Finally, for both stereotactic and MR-guided bi-opsies, there is a weight restriction for the biopsy table, and the patient must be able to fit into the MR gantry.

For all three biopsy techniques, gen-tle handling of the biopsy specimens is necessary to avoid disruption and frag-mentation of the tissue. In the case of stereotactic biopsy, specimen radio-graphs are usually obtained by laying the tissue on a moist paper or petri dish. The tissue samples are then placed in a 10% formalin solution with patient iden-tification. Specimens from US- and MR-guided biopsies are immediately placed in formalin for transportation to the pa-thology suite.

The biopsy procedure for men is per-formed in the same manner as for women. Most male breast cancer mani-fests as a mass and is amenable to US-guided biopsy. Because of the small size of the male breast, stereotactic and MR-guided biopsies are more difficult.

Stereotactic BiopsyIndications.—A stereotactic tech-

nique is used to guide biopsy of suspi-cious (Breast Imaging and Reporting Data Systems [BI-RADS] category 4) or highly suspicious (BI-RADS category 5) lesions seen only, or most conspicuously, on mammograms (33). This primarily includes suspicious microcalcifications, but it also includes masses, asymmetries, or areas of architectural distortion not identified at US. If multiple suspicious findings are present, biopsy of as many targets as are needed to outline the full extent of malignant disease and direct management should be performed.

Equipment.—X-ray imaging is used for localizing and targeting the lesion. Both dedicated prone tables and up-right systems are available. Most cen-ters use a dedicated table on which the patient is positioned prone, with the index breast placed dependently through an opening in the table. Im-aging and biopsy equipment are located beneath the table (Fig 1). The hori-zontal patient position and the visual barrier to the biopsy equipment for the patient result in less motion and few va-sovagal reactions. How ever, the dedi-cated prone tables require more space and are more costly than the upright al-ternative. In addition, there are weight restrictions for the dedicated tables, and prone positioning may be difficult for

some patients. The upright units are added onto standard mammography equipment, which eliminates the need for a dedicated room or equipment for biopsy purposes only. Therefore, these are less costly systems. Patients may be positioned sitting upright, semireclining, or in a lateral decubitus position, often allowing better access to the most poste-rior breast tissue (Fig 2). How ever, the upright patient is at greater risk for a vasovagal reaction. Both types of systems are effective and can be successfully used for stereotactic biopsy (34,35).

Although early stereotactic biopsies were performed by using spring-loaded CNB devices, the VAD is now the stan-dard choice. The VAD retrieves a larger volume of tissue compared with the spring-loaded device, minimizing the rate of histologic upgrades. The histologic eval uation of microcalcifications can be more problematic than that of masses. Since calcifications represent the most common target for stereotactic biopsy, the greater volume of tissue acquired with the VAD is vital in ensuring a suc-cessful stereotactic biopsy (21,24,36–40).

Technique.—The biopsy needle ap-proach is made by reviewing the mam-mographic images and determining which projection provides the best visu-alization of the lesion and the shortest distance from skin to lesion. The breast is positioned in either the mediolateral or craniocaudal position and is com-pressed such that the target is present within the open window of the compres-sion paddle. A scout view is obtained, providing localization of the lesion in the x- and y-axes. Stereotactic images are then obtained 15° from midline in both the positive and negative directions. The depth of the lesion, or the z-axis coordi-nate, is determined by calculating the parallax shift (apparent shift) of the tar-get on the stereotactic images compared with the target location on the reference, or scout image (Fig 3). It is important to determine whether there is adequate breast tissue to position the needle at the lesion without the needle penetrating the posterior aspect of the breast and striking the image receptor. A distance of more than 4 mm from the needle tip



Figure 1: Dedicated stereotactic breast biopsy table. The patient is positioned prone on the table, with imaging and biopsy equipment located below the table.

Figure 1

Figure 3: Stereotactic biopsy images. (a) Scout image obtained with the x-ray tube perpendicular to the detector shows. The clustered microcalcifications centered in the field of view represent the biopsy target. Paired stereotactic images obtained (b) 115° and (c) 215° from perpendicular resulting in parallax shift of the calci-fications. Paired stereotactic images at (d) 115° and (e) 215° in the prefire position and the needle tip at the cluster of calcifications. (f) Single postbiopsy stereo-tactic image with the needle partially withdrawn demonstrates removal of the targeted calcifications, postbiopsy gas, and a tissue marker.

Figure 3

Figure 2: Add-on stereotactic unit. The patient undergoes biopsy in the up-right or decubitus position.

Figure 2



to the distal surface of the breast is con-sidered adequate, and this distance is called the stroke margin. Once the com-puter coordinates have been determined, the information is transferred from the computer to the stereotactic table, and the biopsy needle is moved into place. Accurate needle placement is confirmed by obtaining additional pre- and postfire paired stereotactic images. Vacuum suc-tion pulls the targeted tissue into the open sample notch of the needle, and the inner cutting cannula shears off the tissue specimen, which is then trans-ported retrograde through the biopsy needle to the collection chamber. The biopsy needle remains in place through-out the procedure, with rotation of the sample notch after each tissue specimen is obtained, allowing multiple contiguous samples to be obtained with a single nee-dle insertion.

The number of samples obtained de-pends on the needle size, with 12 sam-ples being the standard for 10–11-gauge needles, and four samples being the standard for 7–9-gauge needles. In gen-eral, specimens are retrieved by rotating the needle around its 360° radius. How-ever, sampling of one region of the lesion can be achieved by directing the sample notch of the needle to a more specific targeted region. When the targeted le-

Figure 4: Specimen radiograph of CNB tissue samples containing calcifications.

Figure 4 sion contains calcifications, a specimen radiograph is obtained to document the presence of calcifications within the tis-sue cores. It is important to verify that the targeted calcifications have been sampled by comparing the specimen ra-diograph to the initial mammographic images of the calcifications and to esti-mate whether the entire radiographic lesion has been removed (Fig 4). It is helpful to separate and mark the cores containing the calcifications prior to sub-mitting the tissue for pathologic exami-nation. In most cases, a tissue marker is placed at the completion of the biopsy to identify the biopsy site in case of removal of the imaging target and to facilitate fol-low-up on subsequent mammograms. If there is sampling of more than one site, markers of different shapes will facilitate identification of these areas (ie, oval, knot, or ribbon shape). Many markers currently in use consist of a titanium clip, which is MR compatible, embedded in a collagen or polyvicryl material, which is sonographically visible for several weeks. This allows subsequent MR imaging and US-guided preoperative localization in the event of a malignant diagnosis. How-ever, there have been reports of inflam-matory reactions due to collagen-embed-ded markers. Therefore, some centers prefer to use stainless-steel markers, which are also usually MR compatible (41).

Manual compression over the biopsy site for 5 minutes is usually adequate to achieve hemostasis. The skin incision is closed with steri-strips. A postprocedure two-view mammogram is obtained and evaluated to ensure accurate sampling of the target and marker placement (Fig 5). The first postbiopsy mammographic im-age is obtained in the same projection as that used for the biopsy due to the po-tential of delayed accordion effect (42). If marker migration has occurred, either due to the accordion effect upon release of breast compression or to hematoma formation and resultant displacement of breast tissue, this should be carefully outlined in the biopsy report.

Potential Challenges.—A number of potential problems can occur with ste-reotactic biopsy. These include a nega-

tive stroke margin, posterior and axillary lesions, and targeted calcifications not seen at pathologic evaluation.

A patient with thin or small breasts may not have adequate tissue depth after compression to permit the biopsy needle to be positioned for targeting without passing entirely through the breast and striking the image receptor distally. This is termed a negative stroke margin. The same problem arises in the patient with a lesion that lies close to the distal skin surface. There are a number of ap-proaches to remedy a negative stroke margin. First, the planned approach can be changed. With the breast compressed in the orthogonal position, the location of the lesion relative to the skin surface many change sufficiently to allow safe in-sertion of the needle. Alternatively, injec-tion of an additional amount of anes-thetic or saline into the tissues may add sufficient depth to remedy a stroke mar-gin that is only slightly negative. Another option is to position the needle with the sample notch slightly proximal to the tar-geted location. Although this places the lesion in the distal aspect of the sampling notch, rather than centered within the sampling notch, adequate tissue samples of the lesion can still be obtained. Bol-stering the breast is another technique that may be helpful in thin breasts. Com-pression is applied from the nipple to-ward the chest wall with a wide tape, an ace bandage, gauze, or other material to thicken the breast and allow safe inser-tion of the biopsy needle. Manufac turing adaptations that may help alleviate the negative stroke margin include the use of a lateral arm to perform biopsy from an approach orthogonal to the compressed breast (Siemens, Munich, Germany) or 180° rotation of the biopsy device (Ho-logic, Bedford, Mass). Last, the air-gap technique may be used. This involves placing a second compression plate be-tween the distal aspect of the breast and the image receptor, with the open biopsy window of both compression plates in line with the lesion. Once inserted, the needle tip can be identified as it tents the skin at the distal aspect of the breast. Care is taken to not allow the needle tip to pierce the distal skin, but if the needle



does pass through the breast and exits the skin on the opposite side, it enters an air space, rather than striking the image receptor.

Lesions close to the chest wall or high in the axillary tail of the breast may be difficult to sample using the prone ste-reotactic technique. By rolling the pa-tient toward the table aperture and pass-ing the arm and shoulder through the opening, more of the posterior and axil-lary tissues can be brought into the bi-opsy window, allowing successful target-ing.

When a biopsy is performed for mi-crocalcifications, a specimen radiograph should be obtained to confirm the calcifi-cations within the tissue cores. It is help-ful to the pathologist to separate and mark the specific tissue cores that con-tain calcifications. If microcalcifications cannot be found histologically, radio-graphs of the paraffin blocks should be

obtained to direct additional sections for the pathologist, and a polarized lens may be used to identify unstained calcium oxylate crystals. One study (43) showed disappearance of calcifications when tis-sue specimens were preserved in formal-dehyde, presumably due to dissolution of the water-soluble calcium compounds. Consequently, they recommend using non aqueous fixative solutions when core biopsies are performed for microcalcifi-cations.

US-guided Biopsy

Indications.—US-guided biopsy of-fers several advantages over stereotactic and MR imaging-guided biopsy methods. US-guided biopsy is a real-time proce-dure that allows visualization and verifi-cation of accurate targeting and faster procedure times. It requires no breast compression and allows more comfort-able positioning for the patient com-

pared with other methods. Finally, no ionizing radiation is used and there are no modality-based contraindications as compared with MR imaging. Generally, when a suspicious lesion is identified for biopsy, if a sonographic correlate can be identified, US-guided biopsy should be chosen (44,45). Suspicious calcifications usually undergo biopsy with stereotactic guidance. However, calcifications can be identified on US scans obtained with high-frequency transducers, particularly when associated with a mass. In these cases, US-guided biopsy may be per-formed instead of stereotactic biopsy, and specimen radiography should be performed to document calcifications in the tissue cores. US guidance also allows safe core biopsy of suspicious axillary lymph nodes, allowing identification of metastatic nodes preoperatively, thereby eliminating the need for sentinel node biopsy and allowing the surgeon to pro-

Figure 5: Postbiopsy (a) mediolateral and (b) craniocaudal digital mammograms of the left breast show different tissue markers to differentiate between the biopsy sites. Thick arrow 5 clip marker, thin arrow 5 ribbon marker.

Figure 5



Figure 6: Patient positioning for US-guided biopsy. For most lesions in the lateral, superior, or inferior breast, the patient is placed slightly oblique in the contralateral direction with the arm raised over the head.

Figure 6

Figure 7: US image demonstrates good visualiza-tion of the biopsy needle when positioned parallel to the transducer.

Figure 7

ceed directly to axillary dissection, when indicated (Movie [online]).

Equipment.—High-quality scanning is necessary for successful US imaging and biopsy. A linear-array, high-resolu-tion transducer with a center frequency of at least 10 MHz is used (46). A va-riety of biopsy needles are available. Whereas stereotactic biopsies are per-formed with a VAD, automated biopsy needles can also be utilized in US-guided biopsies. These needles work by using a spring-loaded mechanism and a rapid two-step firing action. The inner needle is fired first; it contains a recessed sam-pling notch, which enters the targeted tissue. Second, a hollow cutting cannula fires over the notched needle, shearing off the tissue. These needles require a multipass technique in that the needle must be removed from the breast to ob-tain the tissue sample; then it is retar-geted and refired for each subsequent tissue sample. The most commonly used automated biopsy device for the breast is a 14-gauge needle with a 22-mm throw. Hand-held versions of the VAD are also available for US-guided bi-opsies. The needle is positioned deep to the lesion, pulling the targeted tissue down into the sample notch with vacuum suction. As with stereotactic bi-opsies, VADs allow single insertion, di-rectional sampling, and retrieval of larger tissue cores. However, while the advantages of larger samples have been confirmed when stereotactic guidance is used, it is not validated whether larger

cores are as important for accurate pa-thology results for most lesions that are selected to undergo US-guided biopsy, that is, largely noncalcified masses (47). Nonetheless, many centers have ad-opted the VADs for US-guided biopsies due to their speed and ease of use. In addition, complex lesions containing both cystic and solid components are best sampled by using the VADs. Sam-pling of the solid component is most im-portant for accurate pathology results. If multiple passes are made with a spring-loaded needle, and the fluid com-ponent is drained, the solid portion of the lesion may be difficult to visualize and target sonographically.

Technique.—For a solid lesion, pa-tient positioning for the biopsy depends on the location of the lesion. For lesions located in the superior, lateral, or infe-rior breast, the patient is placed in the supine oblique position. For medially located lesions, the patient is usually po-sitioned supine. The ipsilateral arm is raised over the head to decrease the tissue depth of the breast and tighten the overlying skin. The technologist and the US machine are positioned on one side of the examination table, with the physician on the other side of the table. The patient is positioned on the exami-nation table with the index breast closest to the physician. US imaging is performed to identify the target and plan the needle approach. The skin en-try site is generally 1–2 cm from the edge of the transducer, but will vary de-

pending on the depth of the lesion. The best needle visualization occurs with a needle route parallel to the transducer (Fig 6). As the anesthesia is delivered, the planned entry site, approach, angle, and trajectory of the biopsy needle can be confirmed. A scalpel is used to make a skin nick at the entry site. Although many biopsy needles are sharp enough to penetrate the skin, a dermatotomy provides a cleaner incision and allows a smoother entry into the skin. Although some operators use a coaxial system (48), our preference is not to use any type of introducer. Air introduced through the coaxial system causes arti-facts, and move ment of the introducer, requiring adjustment with each needle pass, counteracts any potential advan-tages of having to target only once.

Once the needle has been inserted, real-time scanning is used to identify the needle tip. With US visualization, the needle is then guided to the lesion. The entire length of the needle and its tip must be visualized to achieve an ac-curate trajectory through the lesion, as well as to avoid inadvertent passage through the chest wall, resulting in a pneumothorax. If the transducer and needle remain parallel, that is, along the same longitudinal axis, the needle will be completely visualized (Fig 7).

With a spring-loaded device, the needle is advanced to the edge of the target. The operator should ensure that there is adequate tissue beyond the le-sion, along the trajectory of the needle,



Figure 8: US-guided CNB. (a) Prefire position image for spring-loaded device shows the needle tip at the edge of the mass. (b) Postfire image shows the needle through the mass.

Figure 8

Figure 9: US-guided biopsy with VAD. (a) Initial image shows the needle positioned inferior to the mass. (b) Subsequent image after several passes shows the mass decreasing in size.

Figure 9 to allow safe firing. A prefire image should be obtained to document posi-tioning. The needle is then fired into the lesion, and an image is obtained demonstrating the needle traversing the lesion on this and all subsequent passes (Fig 8). Determining the adequacy of the samples is accomplished by visualiz-ing air tracts within the lesion and by obtaining firm intact cores. Generally, three to five cores are obtained (49).

If a VAD is used, the needle is posi-tioned along the deep margin of the le-sion. The sample notch is opened, and then needle position is adjusted, if nec-essary, to center the lesion within the opening of the sample notch. As sam-pling proceeds, the lesion becomes vis-ibly smaller as tissue is shaved from the inferior aspect of the lesion (Fig 9). Al-though the goal of the procedure is to obtain a sufficient amount of tissue for accurate histopathologic analysis, the ease and speed with which the samples can be obtained allow the operator to remove most of the lesion, if desired. Although not necessary for diagnosis, this often renders a palpable mass no longer palpable and can simplify imag-ing follow-up for benign results.

Once the operator is confident that adequate tissue has been retrieved, a tis-sue marker should be placed directly in the lesion. The same markers are used as with stereotactic biopsy. All are radi-opaque on mammograms because of the presence of the titanium clip. The clip is MR compatible and can be identified on MR images by a small signal void. How-ever, some clips are not well visualized on US scans. Therefore, markers com-posed of the titanium clip embedded in collagen or polyvicryl material are rec-ommended. When a marker is deployed, a postprocedure mammogram is ob-tained in the orthogonal mediolateral and craniocaudal projections to assess marker placement. This allows confir-mation that the US-identified target cor-responds to the mammographic lesion. In the case of malignant results, marker placement is required for patients un-dergoing neoadjuvant chemotherapy. The presence of a clip ensures that a tar-get for excision remains visible, even if the patient has a complete imaging re-

sponse to therapy. In the case of a be-nign result, the presence of a marker can assure future imagers that the lesion has been previously subjected to biopsy. Marker migration occurs much less fre-quently with US-guided biopsies com-pared with stereotactic biopsies due to the lack of compression. However, any deviation of the marker from the tar-geted lesion should be carefully de-scribed in the biopsy report.

Some lesions require a special ap-proach (50). Biopsy of deep lesions may be difficult, particularly if they lie near the chest wall. A remote skin en-try site can be used to allow a parallel needle approach, but this often re-quires traversing a large distance of tis-sue and may be limited by the length of the device. Another approach is to use a standard entry site, initially directing the needle at a steep angle toward the lesion, and then, as the needle nears the target, flattening the needle so that

it approaches the lesion in a horizontal position.

Targets that lie directly on the pec-toralis muscle or an implant may be el-evated away from these structures by instilling local anesthetic and creating a safe zone (Fig 10). This same technique can be used for very superficial lesions to create space between the skin and anterior surface of the lesion.

In some cases, very dense breast tissue can make needle placement diffi-cult. Use of local anesthetic to “dissect” the tissues can be helpful. In extreme cases, firing and advancing a spring-loaded device in a stepwise manner to-ward the lesion may assist in biopsy needle placement. The needle is insert-ed as far as possible and then is fired to create a path for further needle inser-tion. This technique is repeated until the needle reaches the targeted lesion.

Simple cysts are benign lesions that do not require intervention. However,



aspiration may be performed for symp-tomatic relief. Since the purpose is merely to drain the fluid and not to ob-tain tissue for diagnosis, a standard 22-gauge hypodermic needle attached to a 6-mL syringe is used. We do not recommend the use of extension tub-ing. It decreases the amount of nega-tive pressure to the needle and can make aspiration of inspissated cyst contents difficult. Even without tubing, a cyst may be encountered that cannot be completely evacuated. A larger nee-dle may be required, or even a core biopsy needle, to ensure complete evacuation.

If the cyst is completely collapsed at aspiration and yields nonbloody fluid, the fluid is discarded, and the pa-tient is returned to routine follow-up. If bloody fluid is obtained, or the cyst cannot be completely drained, a tissue marker is placed and the fluid is sent for cytologic analysis, or a core biopsy of the residual lesion is performed. If aspiration has been performed to ver-ify concordance between a mammo-graphic mass and the cyst, a postpro-cedure mammogram should be obtained to ensure that the mammo-graphic mass has resolved.

MR-guided BiopsyIndications.—Breast MR imaging is

a highly sensitive technology for detec-tion of breast cancer, commonly finding lesions occult on mammograms and US scans. Using the three-dimen-sional location information from MR imaging, some lesions can be identified

with targeted US and can be sampled by using US guidance. However, this requires a good working knowledge of both modalities, the ability to translate the expected lesion position and ap-pearance from one modality to an-other, and meticulous radiologic-pathologic correlation when the results are returned to ensure that the US finding truly represents the le-sion identified at MR imaging. If the lesion is only visualized with MR im-aging, then MR-guided biopsy is per-formed (51–57).

Equipment.—As with other types of image-guided biopsies, high-quality image acquisition is critical for suc-cessful biopsy completion. There is great variability in imaging protocols and image quality among facilities per-forming MR imaging. However, there are a number of parameters that are considered essential to adequate visu-alization of breast tissue. Magnet strength of 1.5 T or greater is recom-mended. Use of a dedicated breast coil is required. As with stereotactic bi-opsies, use of a VAD is standard prac-tice (58). This maximizes the volume of tissue that can be quickly retrieved and decreases the chance of insuffi-cient tissue. This is especially impor-tant with MR-guided biopsies, in which lesions tend to be smaller than those detected with other modalities. There is no confirmatory method, such as specimen radiography, to ensure sample adequacy, and real-time moni-toring, as occurs with US, is not rou-tinely performed at this time.

Technique.—A team approach is used in performing an MR-guided bi-opsy. Both the interventional technolo-gist from the breast imaging department and the MR technologist are members of the MR imaging biopsy team. The breast interventional technologist is well versed in positioning patients for biopsies, the biopsy device equipment, and the anxiety issues experienced by the patients. His or her assistance in the MR suite is invaluable.

The patient is placed prone on the MR imaging table, with the index breast positioned in the biopsy grid. The loca-tion of the lesion within the breast is known from the original diagnostic MR imaging study, and this information is used to optimally position the breast within the biopsy grid. The breast is minimally compressed between the compression plate and the biopsy grid to prevent motion and to minimize breast deformity during needle place-ment. However, care is taken to not compress the breast enough to impede vascular perfusion of the breast and thus contrast enhancement, potentially interfering with lesion visualization.

Most biopsy systems are designed for the breast to be compressed in the medial-lateral direction, and most le-sions are approached laterally. How-ever, some guidance systems allow a medial approach by working under the table from the contralateral side. On some systems, this can be cumber-some, and lesions posteriorly posi-tioned in the medial breast may not be accessible. If the patient’s body habitus

Figure 10: Creation of a safety zone prior to US-guided biopsy of a mass abutting the pectoral muscle. (a) US image of a small mass positioned against the pectoral muscle. (b) US image of the anesthetic needle inserted posterior to the mass. The anesthetic will lift the mass away from the pectoral muscle, facilitating safe biopsy.

Figure 10



Figure 11: Positioning for MR-guided biopsy. The breast is compressed in the biopsy grid, and a fiducial is placed in the central posterior grid opening.

Figure 11 permits, we prefer to position the torso obliquely and place the index breast in the contralateral breast coil opening, which permits a lateral approach to a medial lesion. In addition, newer coils also allow a craniocaudal approach to the breast.

A fiducial is placed in one of the grid openings, or fiducials built into the bi-opsy grid are used. We usually place the fiducial in the center posterior opening of the grid (Fig 11). Precon-trast images are then obtained. By us-ing landmarks from the original MR imaging study, the expected location of the lesion can be determined and con-firmed to lie within the confines of the biopsy grid. If neces sary, adjustments in positioning can be made prior to contrast material injection.

We use an abbreviated, but other-wise similar, scanning protocol for the biopsy scan as is used for diagnostic MR imaging. By replicating the diagnos-tic imaging technique, we have better success in re-identifying the lesion. Nonetheless, in approximately 12% of cases, nonvisualization of the target oc-curs at the time of planned biopsy (55). Delayed images are obtained, and it is important to ensure that there is no over compression of the breast interfer-ing with perfusion. Subtraction images may be helpful in identifying small or subtle lesions. If the lesion is still not demonstrated, it is usually attributed to normal hormonal changes in the breast, which have resolved at a different point in the menstrual cycle. However, short-term follow-up is recommended in these cases, usually at 6 months.

Once the lesion is confidently identi-fied on the postcontrast images, it can be targeted by various methods. Most simply, a cursor is placed on the lesion on the computer monitor and the im-ages are scrolled back to the grid image and the fiducial. The appropriate bi-opsy grid opening for the needle inser-tion is then determined by comparing the grid opening marking the lesion and the location of the fiducial. Because of differences in the orientation of the breast displayed on the monitor and the position of the patient, it is important to determine these differences in ana-

tomic terms (eg, caudad/cephalad, to-ward nipple/toward chest, rather than left/right, up/down). The specific por-tion of the grid opening needed for needle placement is determined by where the cursor lies within the open-ing (eg, in the center of the opening, in a corner, etc). Finally, the depth of the needle insertion is calculated by sub-tracting the fiducial slice number from the lesion slice number and adding 2 cm to account for the depth of the stan-dard biopsy grid. If more than one le-sion is to undergo biopsy the targeting process is performed for both loca-tions, carefully distinguishing between the lesions and performing the biopsy steps sequentially. Computer-aided de-tection sys tems are available that auto-matically perform these calculations and depict the appropriate grid opening and location pictorially.

Once the lesion is identified and the needle insertion site is determined, a sharp metal trocar is inserted, through a plastic introducer sheath, into the breast to the measured depth. The tro-car is removed and replaced with a plastic obturator to allow scanning. The tip of the obturator corresponds to the center of the needle’s sample notch and should lie at the center of the le-sion on the prebiopsy images. We gen-erally target the lesion along the nipple aspect, allowing gravity and the vac-uum device to pull the lesion down into the sample notch. Sagittal images will show the obturator in cross-section as

a dot that ends at the lesion. Axial im-ages will show the obturator along its full length and are useful in ensuring adequate breast tissue beyond the le-sion and the planned needle position (Fig 12).

Once adequate positioning of the obturator is confirmed, the obturator is removed and the biopsy needle is placed through the stationary intro-ducer sheath. Most biopsy procedures are performed with a 7–9-gauge needle and four to six tissue specimens are obtained. Then, the needle is ex-changed, through the introducer, for the obturator, and postbiopsy images are obtained. Although the tissue re-trieval portion of the biopsy procedure occurs quickly, the overall procedure is scheduled for 1 hour to allow screening for MR imaging safety, informed con-sent, insertion of the intravenous cath-eter, positioning, scanning, and the bi-opsy procedure. Removal or partial removal of the lesion helps confirm ac-curate targeting, although washout of contrast material may falsely appear as complete removal of the lesion. Use of landmarks within the breast and relat-ing them to the position of the gas cav-ity is the most useful method of con-firming accurate sampling. We always place a tissue marker after MR-guided biopsy, even if there is visible lesion re-maining. Any subsequent intervention can then be performed with mammo-graphic or US guidance, and follow-up for benign lesions will be facilitated.



Figure 12: T1-weighted MR images of the obturator used in MR-guided biopsy. (a) On sagittal image, the obturator is seen in cross-section as a high-signal-intensity dot. (b) On axial image, the obturator is seen along its length as a high-signal-intensity line.

Figure 12

Postprocedure ConsiderationsAt the completion of each biopsy, hemo-stasis is achieved with manual compres-sion, usually for 5 minutes. A postpro-cedure mammogram is obtained, and a sterile dressing is applied to the wound. The patient is instructed about normal postbiopsy sequelae (minor pain and bruising), given contact numbers for any concerns or problems, and is in-formed about how and when she or he will receive the biopsy results.

Tissue samples are placed in preser-vative and hand-delivered to pathology department. Accurate specimen label-ing is critical, particularly if there has been biopsy from more than one site. It is important to communicate with the pathologist regarding the type of lesion (mass, distortion, calcifications) and the likelihood of malignancy. By using the American College of Radiology Breast Imaging Reporting and Data System, the level of suspicion can be indicated as 4A, low suspicion for malignancy, 4B, moderate suspicion, 4C high suspicion, and 5, extremely high suspicion for ma-lignancy.

A written report of the procedure should be constructed that describes

the type of lesion and its location, the imaging method used for guidance, the biopsy device used, the number of tis-sue specimens obtained, whether a tis-sue marker was placed, whether any complications occurred during the pro-cedure, and the results of the postbiop-sy mammogram, including the relation-ship of the tissue marker to the index lesion. The procedure report is amend-ed when the pathology results are re-turned, with either concordance or dis-cordance noted, and further management recommendations are out-lined. If discordant results are returned, arrangements for repeat image guided biopsy or surgical biopsy should be made. If the pathology results are malig-nant, review of the entire case should be performed, including both the index and opposite breast, to determine if other findings now require closer scru-tiny and additional intervention. For pa-tients with malignant and high-risk re-sults, arrangements for surgical consultation are made. Benign concor-dant results are generally followed with 6-month imaging. It is best for the phy-sician who performed the biopsy to take responsibility for informing the patient

of her biopsy results. Follow-up recom-mendations can be discussed with the patient at that time as well.

Summary

Image-guided percutaneous breast bi-opsy is a safe, accurate, and cost-effec-tive method of establishing a tissue di-agnosis of breast abnormalities. It has replaced surgical biopsy as the initial method of diagnosis for most breast le-sions, obviating surgery when benign pathology results are demonstrated or allowing for definitive single-stage surgi-cal treatment in most malignant cases.

Stereotactic, US, and MR guidance are all effective methods for performing image-guided biopsy. However, US-guided biopsy is the preferred method due to its speed, cost, patient comfort, and real-time capabilities. With all bi-opsy methods, careful attention to tech-nique and radiologic-pathologic concor-dance are needed for a successful outcome.

Disclosures of Conflicts of Interest: M.C.M. Financial activities related to the present article: none to disclose. Financial activities not related to the present article: author served on Hologic Scientific Advisory Board, received consultancy



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18. Gutwein LG, Ang DN, Liu H, et al. Utiliza-tion of minimally invasive breast biopsy for the evaluation of suspicious breast lesions. Am J Surg 2011;202(2):127–132.

19. Levin DC, Parker L, Schwartz GF, Rao VM. Percutaneous needle vs surgical breast bi-opsy: previous allegations of overuse of sur-gery are in error. J Am Coll Radiol 2012; 9(2):137–140.

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fees and payment for lectures including service on speakers bureaus from Ethicon Endo-Sur-gery, payment for lectures including service on speakers bureaus from Seno-Rx, and institution received money from Research Agreement Na-viscan and Hologic. Other relationships: none to disclose. M.S.N. Financial activities related to the present article: none to disclose. Financial activities not related to the present article: au-thor received payment for lectures including ser-vice on speakers bureaus as well as reimburse-ment for travel to attend ACR committee meeting from American College of Radiology, reimbursement for travel to attend AMCLC meeting from Georgia Radiological Society, and reimbursement for travel to attend ABR meeting from American Board of Radiology. Other rela-tionships: none to disclose.

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