AJR 2000; 175:1353-1355
© American Roentgen Ray Society
Sonographically Guided Metallic Clip Placement After Core Needle Biopsy of the Breast
Stephen W. Phillips1,
Helena Gabriel1,2,
Christopher E. Comstock1,3 and
Luz A. Venta1,4
1
Northwestern University, Lynn Sage Comprehensive Breast Center, 201 E. Huron
St., Chicago, IL 60611.
2
Department of Radiology, Northwestern University Medical School, 675 N. St.
Claire, Ste. 800, Chicago, IL 60611.
3
Present address: Center for Breast Care, 420 Williams, #1000, River Forest, IL
60305.
4
Present address: Methodist-Baylor Breast Center, 6550 Fannin St., Ste. 701, MS
7V9, Houston, TX 77030.
Received December 10, 1999;
accepted after revision March 31, 2000.
Presented at the annual meeting of the American Roentgen Ray Society, New
Orleans, May 1999.
Address correspondence to H. Gabriel.
Introduction
As a result of advances in sonography, breast imagers can now see smaller
and more subtle lesions on sonography. These lesions can take the form of
subtle areas of persistent posterior acoustic shadowing or masses. They can be
difficult to reidentify, particularly after core needle biopsy, because the
lesion may be altered and be made even less conspicuous. This scenario
necessitates a means of marking these lesions after biopsy if a diagnosis of
atypia or malignancy is retrieved on core biopsy and subsequent mammographic
grid hookwire needle localization is required. The use of a small clip for
this purpose has proven to be useful in stereotactic core biopsies
[1,
2]. We describe a method of
deploying a small clip during the sonographically guided biopsy to mark the
biopsy site. This technique is used with conventional sonographically guided
biopsy (14-gauge coaxial automatic gun device) and with modified materials
commonly used for tissue marking in stereotactic vacuum-assisted breast
biopsy. The procedure provides a fast and simple means of accurately marking
the biopsy site for subsequent localization and surgical excision.
Materials and Methods
Technique
The procedure requires that the sonographically guided core needle biopsy
be performed using the coaxial approach first described by Kaplan et al.
[3]. A 13-gauge introducer
trocar is placed under real-time sonographic guidance at the edge of the
lesion. Multiple passes are made with a conventional 14-gauge automatic core
biopsy needle through the introducer. The 14-gauge needle is removed, and the
introducer trocar remains with its tip at the margin of the biopsied
lesion.
The sonography clip is created through a modification of a commercially
available stereotactic clip (Micromark; Biopsys Medical, Irvine, CA). This is
most easily done with the first generation of clips although it can also be
performed with slightly more difficulty using the newer generation clips, but
only if a short introducer is used. The overlying plastic introducer sheath is
first disengaged at the hub by either gently tugging or cutting the sheath
with a scalpel. This marker clip assembly without the overlying sheath now
represents the modified marker clip assembly, which is placed through the
previously positioned introducer trocar that lies adjacent to the biopsied
lesion (Fig.
1A,1B,1C).
Under sonographic guidance, the tip of the modified marker assembly is
extended through the introducer tip and into the lesion. This clip assembly is
easily seen under sonographic guidance. The deployment grip is then squeezed
between the thumb and forefinger in a rapid motion, which frees the clip from
the assembly to attach to tissue at the biopsy site. After deployment,
longitudinal and transverse sonograms and mediolateral and craniocaudal
mammograms are obtained on all patients.
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Fig. 1A. —Modification of stereotactic clip. Photograph of 13-gauge
introducer through which biopsy is performed with 14-gauge biopsy gun. After
biopsy, modified clip will also be placed through introducer.
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Patients
Eleven patients who were 41-71 years old underwent sonographically guided
clip placement. All patients first underwent diagnostic mammography,
sonography, and sonographically guided core needle biopsy using the coaxial
system already described. During deployment, the conspicuity of the clip
assembly, clip prongs, and deployed clip was also evaluated. The accuracy of
clip placement was assessed on the mammograms and sonograms obtained after
deployment by measuring the distance between the clip and any portion of the
lesion on sonography and mammography. The mammographic distance was measured
by averaging the millimeters of displacement on the mediolateral and
craniocaudal images between the clip and lesion. The distance of the clip
relative to the lesion was also measured on specimen radiographs in patients
with malignancies who underwent lumpectomy. The usefulness of the clip as a
guide for retargeting in preoperative hookwire needle localization was also
assessed.
Results
Sonography was most often performed to confirm a questionable or subtle
mammographic finding. Although at times more conspicuous, the lesions
identified on sonography were often themselves subtle or incidental findings.
The average size of the sonographic mass was 5.1 mm, and the sonographic
appearance was that of a hypoechoic mass with shadowing in six patients and an
irregularly marginated mass in five.
Results of sonographically guided core needle biopsy were benign in six
patients: fibrocystic change and fibrosis (n = 2), cyst wall and
fibrosis (n = 2), cyst wall (n = 1), and stromal fibrosis
(n = 1). A malignant diagnosis was obtained in five patients:
infiltrating ductal carcinoma, grade 1 (n = 4) and infiltrating
lobular carcinoma, grade 1 (n = 1).
Clip deployment was successful in all patients. Clip conspicuity was
excellent during the procedure, with the clip prongs convincingly and
consistently visible in all patients (Figs.
2A,2B
and 3). After deployment, the
clip could be identified but was thought to be less clearly seen. The success
of clip placement, as assessed by millimeter displacement between the lesion
and clip, was high sonographically, with 0 mm of displacement. In the six
patients in whom mammographic correlation could be assessed, the displacement
ranged from 0 to 4 mm between the clip and the lesion, with an average
difference of 0.75 mm between the sites measured on the mediolateral and those
measured on the craniocaudal images.
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Fig. 2A. —45-year-old woman with mass suspicious for carcinoma who
underwent breast biopsy with sonographically guided metallic clip. Sonogram
shows hypoechoic shadowing mass that corresponded to questionable mammographic
abnormality. Pathology report from sonographically guided core needle biopsy
revealed fibrosis.
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Fig. 2B. —45-year-old woman with mass suspicious for carcinoma who
underwent breast biopsy with sonographically guided metallic clip. Sonogram
obtained after clip deployment in same patient shows small echogenic focus
that represents clip (arrow) in mass.
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Malignant diagnoses required preoperative hookwire needle localization in
five patients. Three localizations were performed mammographically and two
with sonography guidance. The clip had great usefulness in aiding localization
in four patients by mammographic grid technique. In one patient, the clip
could not be seen on sonography, but lesion conspicuity remained high and
sonographic localization was performed. The biopsy site was identified in all
patients on specimen radiography. The displacement of the clip relative to the
lesion ranged from 0 to 3 mm, with an average of 0.75 mm. The overall average
displacement of the clip relative to the lesion, as seen on mammograms
obtained after deployment and specimen radiographs in eight patients, was 1.1
mm.
Discussion
Sonographically guided clip placement is particularly helpful in the subset
of patients represented by our small series—specifically, patients with
small and subtle mammographic and sonographic lesions. The average size of
lesions targeted on sonography in our series was 5.1 mm. Many of the
mammographic lesions were subtle, and sonography was helpful in confirming and
localizing them from two views. In three patients, the initially subtle
lesions identified on sonography became even less conspicuous after core
needle biopsy.
The technique and procedure are easy and require just a simple modification
of an available apparatus. Conspicuity of the clip and, specifically, the clip
prongs, is excellent before and during deployment. Visualization of the clip
is more difficult, however, after the clip is deployed and the marker assembly
is removed; two patients required mammographic grid needle localization
because the clip was not well seen for localization on sonography. The lesion
of one of the patients was localized sonographically by visualizing the lesion
itself, whereas targeting the clip mammographically localized the other. The
greatest usefulness of the clip, therefore, appears to be in marking the
lesion for retargeting with mammographic guidance.
The literature addressing the accuracy of stereotactically placed clips
cites average displacement of 5-10 mm
[4,
5]. The accuracy of
sonograhically guided clips, therefore, appears to be better (average
accuracy, 1.1 mm). This result is intuitive because the procedure is performed
in real time. Also, the biopsy cavity is smaller with a 14-gauge automatic gun
than it is with an 11-gauge Mammotome (Ethicon Endo-Surgery, Cincinnati, OH),
which may restrict movement of the clip. This technique has been described in
the literature as a means to mark the tumor bed before treatment in the
setting of treatment with induction chemotherapy
[6,7,8,9,10,11].
To our knowledge, this technique has not been described in conjunction with
sonographically guided core needle biopsy. With biopsy using a coaxial
technique, clip placement does not require a separate needle pass but simply
deployment of the clip within the previously placed introducer.
One limitation of this technique is that the stereotactic clip apparatus
most amenable to this modification is the first generation of clips, which has
now been replaced by later generations. The newer clips can be modified;
however, only the more distal part of the plastic sheath can be removed, and
this requires cutting the outer sheath with a scalpel and the use of a short
introducer needle. Perhaps our study will serve as an impetus for the
development of a dedicated clip to be used with sonographic guidance.
In conclusion, sonographically guided metallic clip placement is an easy
successful technique for use after conventional core needle biopsy. The
technique requires a simple modification of the stereotactic clip assembly
unit. This procedure is particularly helpful in marking the biopsy sites of
small subtle masses, lesions that become less conspicuous after core biopsy,
lesions not well seen mammographically, and lesions needing follow-up. The
technique is accurate and provides helpful localization guidance for
retargeting lesions.
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Introduction
Materials and Methods
