Mammographic and Ultrasound-Guided Breast Biopsy Procedures

Prebiopsy Patient Workup

Suspicious nonpalpable, imaging-detected breast lesions can be sampled by either percutaneous needle biopsy or preoperative localization and surgical removal for diagnosis and patient treatment planning. The decision to start with needle biopsy or operation depends on the patient’s clinical situation and requires discussions between the patient, the surgeon, and the radiologist. There is a strong trend toward using needle biopsy before surgery for diagnosis, reserving breast surgery for definitive therapy.

Whether planning biopsy on x-ray mammography, stereotactic targeting, or planning to scan by US, the finding must be seen in craniocaudal (CC) and mediolateral (ML) orthogonal views ( Box 6.1 ). If not seen definitively on CC and ML views, the radiologist triangulates the lesion with the fine-detail mammographic views described in Chapter 2 . Alternatively, stereotactic targeting, tomosynthesis, MRI, and US methods may help determine whether the lesion is real and find its location in the breast.

Nothing substitutes for thorough imaging workups when targeting nonpalpable findings for biopsy. The radiologist must have the lesion’s location firmly entrenched in his or her mind to successfully and safely plan a biopsy. Do not attempt to biopsy a breast lesion if you do not know if the lesion is real or if the location of the lesion is unknown.

Suboptimal workup results in procedure cancellation. reported that stereotactic biopsy cancellation in 16% of cases examined (89/572) occurred mostly because of incomplete workup or inaccurate clinical history. reported cancellation of stereotactic biopsy in only 2% (29/1809) of cases; their low cancellation rates were caused by both improved workups and using advanced stereotactic biopsy techniques. An example of a workup preventing biopsy is skin calcifications. Their peripheral location and radiolucent centers are clues to their location in the skin, and tangential views could identify them as dermal calcifications, avoiding the recommendation for biopsy in the first place.

Aside from a visible and correctly localized target, a checklist of prerequisites for safe and accurate biopsies follows: a patient’s ability to cooperate and hold still during the procedure, blood-thinning medications have been avoided if possible, no allergies to procedure medications, an ability to follow postbiopsy instructions to diminish bleeding and other complications, and the patient’s likelihood to be compliant with postbiopsy follow-up imaging regimens or instructions (see Box 6.1 ).

Informed Consent

Informed consent is an important part of any procedure ( Box 6.2 ). For percutaneous needle biopsy, the radiologist informs the patient of the risks, benefits, and alternatives to percutaneous biopsy (eg, surgical biopsy), as well as the risks and benefits of any alternatives, and that occasionally the target may not be removed or sampled. The most common complication after core or vacuum needle biopsy is hematoma formation, but it is rarely significant. Other rare complications include untoward bleeding (very rarely requiring surgical intervention), infection (with mastitis it is a very rare complication), pneumothorax, pseudoaneurysm formation, implant rupture, milk fistula (if the patient is pregnant or nursing), and vasovagal reactions (see Box 6.2 ). The patient is informed that surgical excision may be needed if the biopsy reveals a malignancy, high-risk lesion, or discordant benign lesion, or if the needle biopsy cannot be completed because of technical limitations (see Box 6.2 ). The patient is informed that a postbiopsy metallic marker will be placed in the biopsy site to guide further surgery and to correlate with other imaging, and that the marker occasionally moves to another location. Last, the patient is given postbiopsy wound management instructions, what to expect and how to manage pain or bleeding, phone numbers to call for untoward complications, and when and how to obtain biopsy results.

For preoperative needle localization, the surgeon obtains informed consent for preoperative needle localization and surgical excision. The radiologist confirms that the patient is properly informed about the needle localization portion of the procedure.

Skin Sterilization, Local Anesthesia, and Skin Incisions

The breast skin is sterilized with a cleansing agent before anesthetic needle insertion. These agents are usually alcohol or iodine based. Most facilities routinely use local anesthesia for percutaneous needle biopsy and preoperative needle localization. A common local anesthetic for breast biopsies is 1% lidocaine in a 10:1 ratio. The lidocaine is given without epinephrine in the skin and subcutaneous tissue (to avoid skin necrosis) and with 1:100,000 epinephrine in the deeper tissue (to increase hemostasis and prolong the anesthetic effect). To avoid mix-ups, the two solutions may be drawn up in different-sized syringes, with a 25-gauge skin injection needle placed only on the syringe containing plain lidocaine, and a longer needle placed only on the syringe containing the lidocaine with 1:100,000 epinephrine. Each syringe is labeled with its contents. The maximum dose of 1% lidocaine with epinephrine is 7 mg/kg (3.5 mg/lb) body weight, not to exceed 500 mg. This translates to 50 mL in a 70-kg patient. The maximum dose of 1% lidocaine without epinephrine is 4.5 mg/kg (2 mg/lb), not to exceed 300 mg. This translates to 30 mL in a 70-kg patient.

A small skin incision made with a scalpel facilitates insertion of the larger needles used for core needle biopsy. Some large-bore needles are extremely sharp and do not need a separate skin incision. Skin incisions usually are not needed for fine-needle aspirations (FNAs) or preoperative localizing needles.

Biopsy Needle Types

Biopsy needle types used for specific breast lesions and guidance methods vary around the world. A trend toward progressively larger needles and more tissue samples per biopsy site has been noted, especially in the United States. Three main types of needles are used for percutaneous biopsies ( Table 6.1 ).

Fine-needle aspiration (FNA) needles are usually 25- to 20-gauge, and are used for cyst aspirations and for solid breast masses. The aspirated material requires interpretation by expert cytopathologists. FNA is usually done with US or palpation guidance with at least four needle passes. It is less commonly done in the United States compared with Europe and Asia.

Automated 18- to 14-gauge large-core (core) needles ( Fig. 6.1 A–B ) are used most often to biopsy masses with US or palpation guidance, with the 14-gauge automated core biopsy needle first introduced by . Many facilities, especially outside the United States, use automated core needles to biopsy masses or calcifications with stereotactic guidance as well. An automated large-core biopsy needle obtains a single tissue biopsy specimen with each pass of the needle. Because separate, repetitive insertions are required for each sample, a coaxial device (trocar and sheath) to gain repeat access to the lesion (especially with US) is often used. Each specimen measures between 15 and 22 mm long depending on the needle, and the width depends on the needle gauge (width). The radiologist obtains samples by firing the needle into the lesion and removing the needle/sample each time to obtain between 2 and 12 specimens. Pathologists who are comfortable interpreting surgically excised breast biopsy tissue also can interpret the core biopsy histologic material.

Directional 7- to 14-gauge vacuum-assisted (vacuum) needles ( Fig. 6.1C ) are used for stereotactic, US-guided, and MRI-guided biopsies. The vacuum needle was first introduced by . Depending on the manufacturer, vacuum biopsy can be done with just one needle pass, with samples measuring up to approximately 2 cm in length and a 4 mm in diameter depending on the gauge of the needle. Specimens are obtained by placing the needle collection aperture of the needle at or in the target by imaging guidance. Specimen collection occurs with the external part of the needle remaining stationary outside of the breast while the cutting part of the needle extracts the samples inside the breast and then vacuums them out to an external collecting chamber. The radiologist points the vacuuming aperture at the target or rotates the aperture within the lesion. Vacuum-assisted devices have the advantage of obtaining larger samples than automated core biopsy sample devices, leading to greater confidence in the diagnosis. For stereotactic guidance, between 6 and 18 specimens are usually obtained, whereas fewer samples may be obtained with US because real-time imaging guides the biopsy. In some facilities, single insertion vacuum biopsies are used to excise benign lesions, such as fibroadenomas previously diagnosed by core needle biopsy, to avoid the need for surgical excision or imaging follow-up.

Other directional vacuum-assisted needles obtain single vacuum specimens with each pass, requiring multiple insertions, similar to the automated large-core needles. These single-insertion vacuum devices have the advantage of obtaining larger samples than automated needles, use smaller handpieces, and may be used with coaxial devices to access the lesion.

Both single-insertion and multiinsertion needles can be used with or without a coaxial guide. Coaxial guides are usually used with US or MRI guidance. The coaxial guide provides a needle path to the target without retraumatizing the breast tissue and consists of an inner sharp stylet and an outer sheath. The radiologist places the coaxial device through the tissue so that the stylet tip/sheath edge is at or in the lesion. Then the radiologist removes the stylet, leaving a sheath that provides a “tunnel” through the breast tissue directly to the lesion. This means the biopsy needle probe may be placed in the lesion to take samples (through the sheath) without having to disturb the surrounding breast tissue. Coaxial biopsies can be done with the sheath placed next to the mass so the needle can fire through the mass ( Fig. 6.2A ) or with the sheath placed through the mass so that the open trough of the needle may be uncovered while already in the mass to sample it ( Fig. 6.2B ).

Cyst Aspiration

Masses on mammograms often prompt requests for breast US and aspiration to see if the mass is a cyst. To do a cyst aspiration, the radiologist advances a fine needle into the cyst by palpation or imaging guidance. If the cyst is tense, fluid immediately wells up into the needle hub. If no fluid is seen, the radiologist attaches a syringe to the needle and draws fluid into the syringe until no more fluid can be obtained. If cyst aspiration is done by US, the cyst will disappear in real time ( Fig. 6.3 ). Alternatively, and less commonly, cyst aspiration can be done by x-ray guidance using a fenestrated compression plate and mammography. If the cyst fluid is clear, yellow, blue, or green, it is normal and is discarded.

Aspirated fluid is sent for cytologic evaluation only if there is an intracystic mass or if the fluid is bloody. A large series of cyst aspirations by showed that cyst fluid cytology is often falsely negative, even in the presence of an intracystic mass. In these cases, the pneumocystogram was enough to diagnose an intracystic mass and prompt biopsy of the rare intracystic cancer. Currently, an intracystic mass should be evident on US, and one can decide to do a core biopsy instead of fine-needle biopsy.

If the cyst fluid is bloody, a marker may be placed into the biopsy cavity so that the location of the biopsy can be identified ( ). If cytology is positive, biopsy or surgical excision can be obtained with the marker used as guidance. If the cytology is negative, surgical consultation and follow-up with US and diagnostic mammography 1 to 2 years for stability may be obtained.

A pneumocystogram is a mammogram obtained after a radiologist injects air into a cyst cavity following cyst aspiration. The pneumocystogram of an air-filled cyst cavity on the mammogram proves that a mass prompting biopsy on the mammogram corresponds to an aspirated cyst, excludes an intracystic mass, and is thought to be therapeutic in preventing cyst recurrence ( Fig. 6.4 ). To do a pneumocystogram, the radiologist aspirates the cyst completely first, then disengages the syringe while carefully holding the needle tip in the decompressed, flattened cyst cavity. The radiologist attaches an air-filled syringe to the needle, injects a small amount of air into the cyst cavity, removes the needle, and immediately obtains CC and ML mammograms. A normal pneumocystogram should show an air-filled, thin-walled, round, or oval cavity without intracystic solid masses or mural nodules.

Usually, postaspiration mammograms are done to see if the cyst disappears, whether it is injected with air or not. The mass prompting the cyst aspiration should resolve after aspiration. If the mass persists on the postaspiration mammogram, the mammographic mass is separate from the aspirated cyst and needs further investigation.

Palpation Guidance

Both FNA or core biopsy can be performed on palpable masses. With this method, the radiologist or surgeon reviews the CC and ML mammograms and other imaging studies, but there is no visualization of the lesion or needle during the procedure. Palpation-guided procedures are similar to US-guided procedures. The lesion must be discretely palpable and held well away from the chest wall for the biopsy to be done with accuracy and safety. This procedure is usually reserved for cysts and solid masses that are almost definitely malignant or benign by imaging and palpation criteria.

Ultrasound Guidance

Compared with stereotactic biopsy, US-guided biopsy has the advantage of using readily available equipment and is fast and cost-effective. In the clinic, US is often used on palpable masses to see if they are cysts. If the mass is solid, US determines whether the mass is far enough from the chest wall or other important structures for image-guided or palpation-guided biopsy.

Nonpalpable mammographic masses often prompt US studies to target them for biopsy. When correlating a mammographic mass to the US, the mass may move quite a bit from the upright mammogram to the supine US because the breast falls dependently onto the chest wall when the patient lies down. Thus one can understand why the mass can be far away from the chest wall on the mammogram and lie next to the pectoralis muscle on the US ( Fig. 6.5 ).

Pneumothorax is an important but preventable complication when planning US-guided needle biopsies. Unlike preoperative x-ray–guided needle localization or prone stereotactic localization, the supine US-guided position may not have a needle trajectory parallel to the chest wall. Further complicating matters, some core biopsy needles throw the cutting trough and needle tip 2.5 cm further into the tissue from their initial position. Thus, planning a safe US needle biopsy trajectory must take into account the needle tip, the needle throw trajectory, and the tissue beyond the tip.

To perform a safe procedure, the radiologist rolls the patient on the table so that the chest wall is as parallel to the floor as possible, so that a needle trajectory will traverse safely through the mass into normal tissue and not angle steeply aiming toward the lungs. Patient positioning may take some time, but it is worth the few minutes to position the patient accurately and avoid pneumothorax. Another way to keep the needle away from the chest wall is to inject anesthetic underneath the targeted mass to lift it away from the pectoralis muscle. Alternatively, in some cases, the radiologist may insert the biopsy needle tip into the mass to lift it into a safer trajectory before firing the needle ( Fig. 6.6 ). Yet another technique is to use a needle that does not use a throw at all, but opens the trough inside the mass to sample it. In any case, the first thing to do is to safely insert the needle into the mass. If the needle cannot be inserted into the mass safely for biopsy, then the mass should be localized and excised instead of sampled percutaneously.

For US-guided FNA, the radiologist introduces a needle in the plane of the transducer axis to show the entire shaft of the needle, its tip, and the lesion. Once the needle is within the lesion, the radiologist aspirates the mass with a vigorous to-and-fro movement to obtain material for cytologic evaluation and then withdraws the needle ( Fig. 6.7 ). At least four passes should be performed; optimally, the material should be analyzed immediately by a cytotechnologist to ensure that adequate cellular material has been obtained for diagnosis. After aspiration, direct pressure is applied to the site.

To perform an automated core biopsy under US guidance, the radiologist localizes the lesion by US and chooses the course of needle insertion that offers the most accuracy and safety. While anesthetizing the core biopsy track under direct US guidance, the radiologist uses the anesthesia needle to get an idea of how dense the breast feels and to see the needle trajectory. The radiologist also calculates the core needle throw to determine where to place the core needle tip “prefire” so the core trough will be in the middle of the lesion “postfire” ( Fig. 6.8 ).

Then, under direct US visualization, the radiologist introduces the automated core biopsy needle into the breast. If the lesion is large enough, the radiologist introduces the needle into the edge of the lesion to hold it in place. Otherwise, the radiologist may choose to fire the needle through the mass with or without a coaxial system ( Fig. 6.9 ). In any case, the radiologist fires the biopsy core needle under direct visualization and removes the needle each time to harvest the cores. Optimally, three to six tissue specimens are obtained from different parts of the mass. After sampling, the radiologist places a metallic marker into the mass, and the technologist holds direct pressure on the breast to establish hemostasis. After hemostasis is established, the technologist bandages the wound and takes orthogonal mammograms to show the marker and any residual mass.

A vacuum biopsy is similar to an automated multifire core biopsy, but the vacuum needle is usually placed under or inside the lesion. The probe “vacuums” tissue into the trough, cuts the sample, and carries it into a container outside the breast. Multiple samples can be obtained with one insertion. During a needle biopsy using vacuum technique, the radiologist obtains several samples, concentrating on aiming the trough at the mass ( Figs. 6.10 and 6.11 ; Video 6.1 ). Afterward, the radiologist may place a marker in the mass either through the probe or by using a marker that is inserted via its own separate needle. This vacuum technique carries a special caveat regarding the skin. If the probe is too close to the skin, the skin can be “vacuumed” into the trough and sampled, causing skin injury, requiring a suture or, in extreme cases, a skin graft.

To do US-guided preoperative needle localization, the radiologist places a 20-gauge needle into the mass or marker under US (similar to the FNA procedure), places a hooked wire through the needle, then removes the needle, takes orthogonal mammograms to show the wire tip and mass/marker, and waits for the excised tissue specimen.