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Published online before print November 22, 2005, 10.1148/radiol.2381050050
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(Radiology 2005;238:54-61.)
© RSNA, 2005

Breast Imaging

MR Imaging–guided 9-gauge Vacuum-assisted Core-Needle Breast Biopsy: Initial Experience1

Susan G. Orel, MD, Mark Rosen, MD, Carolyn Mies, MD and Mitchell D. Schnall, MD

1 From the Departments of Radiology (S.G.O., M.R., M.D.S.) and Pathology and Laboratory Medicine (C.M.), University of Pennsylvania Medical Center, 3400 Spruce St, Philadelphia, PA 19104. From the 2003 RSNA Annual Meeting. Received January 13, 2005; revision requested March 16; revision received April 14; accepted May 9. Address correspondence to S.G.O. (e-mail: orel{at}rad.upenn.edu).


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 
Purpose: To perform magnetic resonance (MR) imaging–compatible vacuum-assisted 9-gauge core-needle biopsy of suspicious enhancing breast lesions identified at MR imaging.

Materials and Methods: The institutional review board granted exempt status for this HIPAA-compliant study and waived the requirement for informed consent. The MR imaging–guided 9-gauge vacuum-assisted core-needle biopsy findings of 85 lesions in 75 patients aged 31–89 years were retrospectively reviewed. The biopsies were performed as part of the patients' clinical care with a Food and Drug Administration–approved biopsy system and not within a research protocol. All included patients had received a diagnosis of malignant, benign, or high-risk (for cancer) breast tissue at core-needle biopsy and had undergone subsequent surgery or follow-up imaging. MR imaging–guided biopsy results were compared with final histopathologic or follow-up imaging findings.

Results: At MR imaging–guided core-needle biopsy, malignancy was identified in 52 (61%) lesions: 35 invasive cancers and 17 ductal carcinoma in situ (DCIS) lesions. Four (24%) of the 17 DCIS lesions were upgraded to invasive cancer at excisional biopsy or mastectomy. A high-risk lesion (ie, atypical ductal hyperplasia, atypical lobular hyperplasia, lobular carcinoma in situ, or radial scar) was identified in 18 (21%) cases. Two (25%) of eight atypical ductal hyperplasia lesions were upgraded to DCIS at excision. No malignancy was found in the atypical lobular hyperplasia (n = 2), lobular carcinoma in situ (n = 5), or radial scar (n = 3) lesions. Fifteen (18%) lesions were found to be benign lesions of unknown type at excision or mastectomy. For 13 of these 15 lesions, the benign results were concordant with the imaging findings. Both (two of 86, 2%) discordant cases represented false-negative lesions. The remaining 13 benign lesions were validated at excisional biopsy (n = 9) or follow-up imaging (n = 4).

Conclusion: Initial experience revealed MR imaging–guided 9-gauge vacuum-assisted core-needle breast biopsy to be a reasonable alternative to MR imaging–guided wire localization of suspicious lesions identified at MR imaging only, on the basis of published information regarding the latter.

© RSNA, 2005


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 
Many investigators have found magnetic resonance (MR) imaging to be highly sensitive for the detection of breast cancer, and both invasive and noninvasive cancers that are occult at mammography, ultrasonography (US), and clinical examination can be detected at MR imaging (1). However, not all enhancing lesions suspicious for malignancy prove to be malignant at biopsy. In reported series of MR imaging–guided wire localization or percutaneous core-needle biopsy of suspicious enhancing lesions, approximately 40%–60% of the lesions proved to be benign (2–6). The limited specificity of MR imaging is due to the overlapping morphologic structures and enhancement kinetics of benign and malignant lesions (1,7–11). Given this overlapping, tissue diagnosis of suspicious enhancing lesions is required to differentiate breast cancer from benign processes.

Some MR imaging–detected lesions are identified at "second-look" US. In a report on the utility of second-look US for the assessment of MR-detected suspicious lesions, a US correlate was identified in 23% of cases, and 43% of the cases were breast cancers. However, 14% of the lesions without a US correlate proved to be cancer (12). Therefore, for MR-detected suspicious lesions that cannot be identified with mammography or US, an MR imaging–compatible interventional system is required for tissue diagnosis.

Until recently, MR imaging–guided wire localization followed by excisional biopsy was the mainstay of MR-guided intervention. Several investigators have demonstrated the usefulness of MR-guided wire localization (2–6). Yet, many limitations of this method have become evident and include access to only the lateral breast with many systems, contrast material washout during the procedure, the inability to document the relative location of the lesion relative to the hook of the wire if non–MR-compatible wires are used, and perhaps most clinically important, the inability to document successful lesion removal because in most cases, the lesion localized with MR imaging guidance is not visible on a mammographic specimen radiograph (1). In addition to these technical limitations, a major downside of MR-guided wire localization followed by excisional biopsy is the cost and morbidity associated with the potentially large number of excisional biopsies that are performed because of MR-detected suspicious enhancing lesions but yield benign results.

Core-needle biopsy performed with mammography and US guidance is a well-established safe, accurate, and cost-effective method of obtaining histologic specimens of suspicious lesions, because a malignant result can reduce the number of subsequent surgical procedures performed and a concordant benign result can obviate surgery (13). Percutaneous MR-compatible core-needle biopsy systems have recently become available, and initial reports on the use of various automated biopsy guns and vacuum-assisted biopsy devices have shown these systems to be safe and effective for tissue retrieval (14–19). The purpose of our study was to perform MR-compatible vacuum-assisted 9-gauge core-needle biopsy of suspicious enhancing breast lesions identified at MR imaging.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 References
 
Our institutional review board granted exempt status for this Health Insurance Portability and Accountability Act–compliant study and waived the requirement for informed consent.

Study Population and Clinical Indications
Between February 2003 and December 2004, 199 women with a total of 217 MR-detected suspicious enhancing lesions underwent MR-guided 9-gauge vacuum-assisted core-needle biopsy (hereafter referred to as MR-guided biopsy). Of the initial group of 199 women, 75 women (mean age, 52 years; age range, 31–89 years) who had a total of 85 suspicious lesions received a diagnosis of malignant, high-risk (for malignancy), or benign tissue at core-needle biopsy and subsequently underwent a surgical procedure or follow-up imaging that revealed the stability, decrease, or resolution of the imaging finding.

The findings of core-needle biopsy were compared with the findings of surgical (76 lesions) or imaging (four lesions) follow-up. Five patients who received a diagnosis of cancer at MR-guided core-needle biopsy underwent no additional surgical procedure: Four patients were treated with chemotherapy, and one refused to undergo surgery. The clinical indications for MR imaging were ipsilateral breast cancer staging (28 lesions), equivocal mammogram or physical examination findings (23 lesions), synchronous contralateral lesion (18 lesions), screening in a high-risk case (known BRCA1 or BRCA2 carrier, >25% lifetime risk, history of lobular carcinoma in situ, or stated but not detailed clinical history of breast cancer) (n = 13), and axillary node malignancy with unknown site of primary tumor (n = 3).

Biopsy Procedure
The MR-guided core-needle biopsies were performed by using a Food and Drug Administration–approved, commercially available MR-compatible core-needle biopsy system (Suros ATEC [Automated Tissue Excision and Collection]; Suros Surgical Systems, Indianapolis, Ind) as part of the patients' clinical care—that is, not within a research protocol. Informed consent for percutaneous core-needle biopsy was obtained from each patient, and an intravenous line was started. The biopsies were performed by one of three radiologists (S.G.O. and M.D.S., with 12 years experience in MR-guided breast intervention; M.R., with 5 years experience in MR-guided breast intervention). Imaging was performed in all patients while they were prone and by using a dedicated breast compression coil (USA Instruments; Aurora, Ohio) fitted with a sterile perforated plate. Two reference markers containing copper sulfate were placed in arbitrary holes in the plate. After the breast was cleansed with povidone iodine solution (Betadine; Purdue Frederick, Norwalk, Conn), the biopsy plate was placed by using gentle compression.

The breast MR imaging sequences used included a transverse T1-weighted localizing sequence followed by a fat-suppressed three-dimensional spoiled gradient-echo sequence (minimum repetition time/minimum echo time, 3-mm section thickness, 512 x 256 imaging matrix, acquisition time of 1 minute 37 seconds) performed before and after intravenous administration of 20 mL of gadodiamide (Omniscan; Amersham Health, Princeton, NJ) plus 10 mL of saline.

The coordinates of the enhancing lesion (superior-to-inferior, anterior-to-posterior, and right-to-left) were identified, and the distance from the nearest reference marker was calculated. An appropriate hole in the perforated plate was chosen, and a local anesthetic was injected: 1% lidocaine hydrochloride to induce dermal and subcutaneous anesthesia and 1% lidocaine with a 1:100 000 dilution of epinephrine to induce deep breast anesthesia. A skin incision was made with a scalpel. The biopsy was performed by using the Suros ATEC biopsy system by one of three radiologists (S.G.O., M.D.S., M.R.) who specialize in breast MR imaging.

The introducer sheath was then placed over the introducer stylet. The depth stop was placed to the appropriate depth, and the stylet was inserted into the breast. The stylet was removed, and the localizing obturator was placed in the sheath. Findings at repeat three-dimensional gradient-echo MR imaging in the sagittal and transverse planes confirmed the location of the obturator relative to the lesion. The obturator was removed, and the 9-gauge vacuum-assisted core needle was placed through the sheath. Multiple contiguous samples were obtained at 360°. The number of core samples obtained was not recorded. Repeat MR imaging was performed to identify postbiopsy changes. In 75 of the 85 lesions sampled at biopsy, a titanium clip attached to a resorbable collagen pledget (MammoMark Biopsy Site Marker; Artemis Medical, Hayward, Calif) was placed to mark the biopsy site. After clip placement, the fast spoiled gradient-echo in the steady state sequence was repeated for clip identification. Postbiopsy mammography was performed in 20 of the 75 patients. Although the lesions sampled at biopsy were not mammographically visible, mammography was performed to identify the location of the clip within the breast for possible mammographically guided wire localization.

Although the time required to perform each biopsy was not prospectively recorded, each biopsy was allotted a 60-minute time slot. In general, the total time required for the MR imaging examination performed before biopsy, the biopsy procedure itself, and the postbiopsy care usually ranged from 30 to 60 minutes. There were no major complications. Any bleeding was controlled with local compression.

Concordance between MR Imaging and Core-Needle Biopsy Findings
In each case, the histologic findings of core-needle biopsy were compared with the MR imaging findings to ensure concordance. Surgical follow-up was recommended for all malignant lesions, all high-risk lesions (atypical ductal hyperplasia [ADH], atypical lobular hyperplasia, and lobular carcinoma in situ), and all benign results that were discordant with the MR imaging findings. The classification of high-risk lesion was based on published experience with mammography- and US-guided core-needle biopsy findings (14). Papillomas were classified as benign lesions; however, this designation remains controversial. In all cases in which follow-up excisional biopsy or mastectomy was performed, the final histopathologic diagnosis—that based on both MR-guided core-needle biopsy findings and either excisional biopsy or mastectomy findings—was compared with the results of MR-guided core-needle biopsy. Upgrades of ADH to ductal carcinoma in situ (DCIS) or of DCIS to invasive cancer at surgery were classified as underestimated findings. Discordant benign histopathologic findings found to be malignant at surgery were classified as false-negative cases. Concordant benign findings were included in this study if verification of the diagnosis was obtained at subsequent excisional biopsy or mastectomy or at follow-up imaging that demonstrated a resolution or decrease in size of the enhancing lesion. Retrospective review was performed by one of the authors (S.G.O.) and included review of the clinical indication for MR imaging, size and morphologic features of the MR imaging finding, histologic results of MR-guided core-needle biopsy, clip placement, postbiopsy mammographic findings, and subsequent surgical or follow-up imaging findings.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 References
 
Lesion Size and Core-Needle Biopsy
Lesion diameters ranged from 5 to 100 mm (mean, 17 mm). Of the 85 lesions sampled at core-needle biopsy, 52 (61%) were malignant (30 invasive ductal cancers, five invasive lobular cancers, and 17 DCIS lesions); 18 (21%), high risk (eight ADH lesions, five lobular carcinoma in situ lesions, three radial scars, and two cases of atypical lobular hyperplasia); and 15 (18%), benign (Table).


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  		Histopathologic Diagnoses of 85 MR Imaging–guided Vacuum Core-Needle Biopsy Findings with Subsequent Surgical or Imaging Follow-up

 
Invasive Cancer
Of the 35 invasive cancers diagnosed at core-needle biopsy, which were 5–100 mm (mean, 14.8 mm) in diameter at MR imaging, 16 were treated with mastectomy and 14 were treated with MR-guided wire localization of the residual enhancing lesion or mammographically guided wire localization of the clip followed by excisional biopsy (Table). The histopathologic findings in these 30 cases were invasive cancer in 26 cases, DCIS in one case, and no residual cancer in three cases. In the remaining five cases, no additional surgery was performed: Four patients underwent chemotherapy, and one patient refused treatment.

DCIS Lesions
Of the 17 DCIS lesions diagnosed at core-needle biopsy, which were 8–60 mm (mean, 27.6 mm) in diameter at MR imaging, 10 were treated with mastectomy and seven were treated with MR imaging– or mammographically guided wire localization and excisional biopsy. Histopathologic findings were DCIS (Fig 1) in nine cases; DCIS with invasive cancer in four cases (0.1, 0.5, 3.0, and 6.0 mm in diameter); and ADH, atypical lobular hyperplasia, lobular carcinoma in situ, or no residual tumor in one case each.



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  		Figure 1a: Palpable subareolar mass and multiple other lesions identified at US in 47-year-old woman. (a) Sagittal fat-suppressed contrast-enhanced three-dimensional fast spoiled gradient-echo in the steady state MR image (repetition time msec/echo time msec, 9.3/2.2) obtained during MR-guided biopsy shows introducer (arrow) within the mass. (b) Corresponding postbiopsy MR image shows decreased size of subareolar mass and area of ductal enhancement (arrow) inferior to subareolar mass. Histopathologic review of core-needle biopsy specimens from subareolar mass (not shown) revealed benign papilloma. (c) Core-needle biopsy specimen from area of ductal enhancement shows sclerosing papilloma partially involved by DCIS (arrows). (Hematoxylin-eosin stain; original magnification, x50.) (d) Magnified core-needle biopsy specimen from area of ductal enhancement shows intermediate-grade DCIS growing in cribriform pattern. (Hematoxylin-eosin stain; original magnification, x200.) Follow-up surgical excision revealed benign papilloma (subareolar mass) and confirmed residual DCIS at site of MR-guided biopsy of area of ductal enhancement. No invasive cancer was found.

 


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  		Figure 1b: Palpable subareolar mass and multiple other lesions identified at US in 47-year-old woman. (a) Sagittal fat-suppressed contrast-enhanced three-dimensional fast spoiled gradient-echo in the steady state MR image (repetition time msec/echo time msec, 9.3/2.2) obtained during MR-guided biopsy shows introducer (arrow) within the mass. (b) Corresponding postbiopsy MR image shows decreased size of subareolar mass and area of ductal enhancement (arrow) inferior to subareolar mass. Histopathologic review of core-needle biopsy specimens from subareolar mass (not shown) revealed benign papilloma. (c) Core-needle biopsy specimen from area of ductal enhancement shows sclerosing papilloma partially involved by DCIS (arrows). (Hematoxylin-eosin stain; original magnification, x50.) (d) Magnified core-needle biopsy specimen from area of ductal enhancement shows intermediate-grade DCIS growing in cribriform pattern. (Hematoxylin-eosin stain; original magnification, x200.) Follow-up surgical excision revealed benign papilloma (subareolar mass) and confirmed residual DCIS at site of MR-guided biopsy of area of ductal enhancement. No invasive cancer was found.

 


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  		Figure 1c: Palpable subareolar mass and multiple other lesions identified at US in 47-year-old woman. (a) Sagittal fat-suppressed contrast-enhanced three-dimensional fast spoiled gradient-echo in the steady state MR image (repetition time msec/echo time msec, 9.3/2.2) obtained during MR-guided biopsy shows introducer (arrow) within the mass. (b) Corresponding postbiopsy MR image shows decreased size of subareolar mass and area of ductal enhancement (arrow) inferior to subareolar mass. Histopathologic review of core-needle biopsy specimens from subareolar mass (not shown) revealed benign papilloma. (c) Core-needle biopsy specimen from area of ductal enhancement shows sclerosing papilloma partially involved by DCIS (arrows). (Hematoxylin-eosin stain; original magnification, x50.) (d) Magnified core-needle biopsy specimen from area of ductal enhancement shows intermediate-grade DCIS growing in cribriform pattern. (Hematoxylin-eosin stain; original magnification, x200.) Follow-up surgical excision revealed benign papilloma (subareolar mass) and confirmed residual DCIS at site of MR-guided biopsy of area of ductal enhancement. No invasive cancer was found.

 


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  		Figure 1d: Palpable subareolar mass and multiple other lesions identified at US in 47-year-old woman. (a) Sagittal fat-suppressed contrast-enhanced three-dimensional fast spoiled gradient-echo in the steady state MR image (repetition time msec/echo time msec, 9.3/2.2) obtained during MR-guided biopsy shows introducer (arrow) within the mass. (b) Corresponding postbiopsy MR image shows decreased size of subareolar mass and area of ductal enhancement (arrow) inferior to subareolar mass. Histopathologic review of core-needle biopsy specimens from subareolar mass (not shown) revealed benign papilloma. (c) Core-needle biopsy specimen from area of ductal enhancement shows sclerosing papilloma partially involved by DCIS (arrows). (Hematoxylin-eosin stain; original magnification, x50.) (d) Magnified core-needle biopsy specimen from area of ductal enhancement shows intermediate-grade DCIS growing in cribriform pattern. (Hematoxylin-eosin stain; original magnification, x200.) Follow-up surgical excision revealed benign papilloma (subareolar mass) and confirmed residual DCIS at site of MR-guided biopsy of area of ductal enhancement. No invasive cancer was found.

 
High-Risk Lesions
Of the 85 lesions, 18 (21%), which were 7–50 mm (mean, 12.5 mm) in diameter at MR imaging, were found to be high risk at core-needle biopsy (Fig 2). Additional surgery was performed in all eight cases in which ADH was found at MR-guided core-needle biopsy. Two (25%) of these eight cases were upgraded to DCIS at excision or mastectomy. No malignancy was found in any of the cases in which atypical lobular hyperplasia, lobular carcinoma in situ, or radial scar was diagnosed at MR-guided core-needle biopsy.



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  		Figure 2a: Findings in 53-year-old woman with newly diagnosed breast cancer at MR imaging screening of contralateral breast. (a) Sagittal fat-suppressed contrast-enhanced three-dimensional fast spoiled gradient-echo in the steady state MR image (9.3/2.2) obtained before biopsy reveals area of linear-regional enhancement with associated architectural distortion (arrows) in superior region of breast. (b) Corresponding MR image obtained during biopsy shows introducer (arrow) within lesion. MR-guided core-needle biopsy specimens show (c) proliferative fibrocystic changes with florid ductal hyperplasia (arrows) (hematoxylin-eosin stain; original magnification, x100) and (d) foci of ADH (arrows) (hematoxylin-eosin stain; original magnification, x200). ADH but no carcinoma was found at subsequent needle localization and excisional biopsy.

 


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  		Figure 2b: Findings in 53-year-old woman with newly diagnosed breast cancer at MR imaging screening of contralateral breast. (a) Sagittal fat-suppressed contrast-enhanced three-dimensional fast spoiled gradient-echo in the steady state MR image (9.3/2.2) obtained before biopsy reveals area of linear-regional enhancement with associated architectural distortion (arrows) in superior region of breast. (b) Corresponding MR image obtained during biopsy shows introducer (arrow) within lesion. MR-guided core-needle biopsy specimens show (c) proliferative fibrocystic changes with florid ductal hyperplasia (arrows) (hematoxylin-eosin stain; original magnification, x100) and (d) foci of ADH (arrows) (hematoxylin-eosin stain; original magnification, x200). ADH but no carcinoma was found at subsequent needle localization and excisional biopsy.

 


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  		Figure 2c: Findings in 53-year-old woman with newly diagnosed breast cancer at MR imaging screening of contralateral breast. (a) Sagittal fat-suppressed contrast-enhanced three-dimensional fast spoiled gradient-echo in the steady state MR image (9.3/2.2) obtained before biopsy reveals area of linear-regional enhancement with associated architectural distortion (arrows) in superior region of breast. (b) Corresponding MR image obtained during biopsy shows introducer (arrow) within lesion. MR-guided core-needle biopsy specimens show (c) proliferative fibrocystic changes with florid ductal hyperplasia (arrows) (hematoxylin-eosin stain; original magnification, x100) and (d) foci of ADH (arrows) (hematoxylin-eosin stain; original magnification, x200). ADH but no carcinoma was found at subsequent needle localization and excisional biopsy.

 


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  		Figure 2d: Findings in 53-year-old woman with newly diagnosed breast cancer at MR imaging screening of contralateral breast. (a) Sagittal fat-suppressed contrast-enhanced three-dimensional fast spoiled gradient-echo in the steady state MR image (9.3/2.2) obtained before biopsy reveals area of linear-regional enhancement with associated architectural distortion (arrows) in superior region of breast. (b) Corresponding MR image obtained during biopsy shows introducer (arrow) within lesion. MR-guided core-needle biopsy specimens show (c) proliferative fibrocystic changes with florid ductal hyperplasia (arrows) (hematoxylin-eosin stain; original magnification, x100) and (d) foci of ADH (arrows) (hematoxylin-eosin stain; original magnification, x200). ADH but no carcinoma was found at subsequent needle localization and excisional biopsy.

 
False-Negative Lesions
Of the total 85 validated cases, two (2%) were false-negative. In both cases, the benign histologic findings at core-needle biopsy were discordant with the MR imaging findings. In one of these two cases, a suspicious 5-mm enhancing mass was identified in the contralateral breast of a patient with newly diagnosed breast cancer (Fig 3). The biopsy procedure was complicated by bleeding at the biopsy site, which obscured the enhancing lesion. Histopathologic review of the core-needle biopsy specimen revealed a microscopic papilloma. On the basis of the discordance in lesion size and the nonsuccessful lesion biopsy, repeat MR imaging was performed the following week. The enhancing lesion was again identified, and MR-guided needle localization was performed. A 6-mm tubular cancer was identified at excisional biopsy. The second false-negative case was complicated by technical difficulty in placing the introducer in the breast. By the time the introducer was placed and biopsy was performed, the lesion, which was 20 mm in diameter, was no longer visible secondary to contrast material washout. Histopathologic analysis revealed fibrocystic changes, but the MR imaging appearance was highly suggestive of malignancy. MR-guided wire localization and excisional biopsy revealed invasive ductal carcinoma.



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  		Figure 3a: Sagittal fat-suppressed contrast-enhanced three-dimensional fast spoiled gradient-echo in the steady state MR images (9.3/2.2) obtained at screening of contralateral breast of 63-year-old woman with newly diagnosed breast cancer. (a) Image obtained before biopsy reveals 5-mm enhancing mass (arrow). (b) Image obtained during core-needle biopsy shows introducer (arrow) within lesion. (c) Image obtained after biopsy shows introducer and a biopsy cavity (arrow). Additional MR images (not shown) demonstrated hematoma formation in medial region of breast. Histopathologic specimens (not shown) revealed small papilloma that was smaller than the MR imaging–detected mass. (d, e) Repeat MR images obtained 1 week later show persistence of enhancing mass (in d) adjacent to the hematoma (arrowhead). MR-guided needle localization and excisional biopsy (not shown) revealed 6-mm invasive tubular cancer.

 


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  		Figure 3b: Sagittal fat-suppressed contrast-enhanced three-dimensional fast spoiled gradient-echo in the steady state MR images (9.3/2.2) obtained at screening of contralateral breast of 63-year-old woman with newly diagnosed breast cancer. (a) Image obtained before biopsy reveals 5-mm enhancing mass (arrow). (b) Image obtained during core-needle biopsy shows introducer (arrow) within lesion. (c) Image obtained after biopsy shows introducer and a biopsy cavity (arrow). Additional MR images (not shown) demonstrated hematoma formation in medial region of breast. Histopathologic specimens (not shown) revealed small papilloma that was smaller than the MR imaging–detected mass. (d, e) Repeat MR images obtained 1 week later show persistence of enhancing mass (in d) adjacent to the hematoma (arrowhead). MR-guided needle localization and excisional biopsy (not shown) revealed 6-mm invasive tubular cancer.

 


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  		Figure 3c: Sagittal fat-suppressed contrast-enhanced three-dimensional fast spoiled gradient-echo in the steady state MR images (9.3/2.2) obtained at screening of contralateral breast of 63-year-old woman with newly diagnosed breast cancer. (a) Image obtained before biopsy reveals 5-mm enhancing mass (arrow). (b) Image obtained during core-needle biopsy shows introducer (arrow) within lesion. (c) Image obtained after biopsy shows introducer and a biopsy cavity (arrow). Additional MR images (not shown) demonstrated hematoma formation in medial region of breast. Histopathologic specimens (not shown) revealed small papilloma that was smaller than the MR imaging–detected mass. (d, e) Repeat MR images obtained 1 week later show persistence of enhancing mass (in d) adjacent to the hematoma (arrowhead). MR-guided needle localization and excisional biopsy (not shown) revealed 6-mm invasive tubular cancer.

 


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  		Figure 3d: Sagittal fat-suppressed contrast-enhanced three-dimensional fast spoiled gradient-echo in the steady state MR images (9.3/2.2) obtained at screening of contralateral breast of 63-year-old woman with newly diagnosed breast cancer. (a) Image obtained before biopsy reveals 5-mm enhancing mass (arrow). (b) Image obtained during core-needle biopsy shows introducer (arrow) within lesion. (c) Image obtained after biopsy shows introducer and a biopsy cavity (arrow). Additional MR images (not shown) demonstrated hematoma formation in medial region of breast. Histopathologic specimens (not shown) revealed small papilloma that was smaller than the MR imaging–detected mass. (d, e) Repeat MR images obtained 1 week later show persistence of enhancing mass (in d) adjacent to the hematoma (arrowhead). MR-guided needle localization and excisional biopsy (not shown) revealed 6-mm invasive tubular cancer.

 


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  		Figure 3e: Sagittal fat-suppressed contrast-enhanced three-dimensional fast spoiled gradient-echo in the steady state MR images (9.3/2.2) obtained at screening of contralateral breast of 63-year-old woman with newly diagnosed breast cancer. (a) Image obtained before biopsy reveals 5-mm enhancing mass (arrow). (b) Image obtained during core-needle biopsy shows introducer (arrow) within lesion. (c) Image obtained after biopsy shows introducer and a biopsy cavity (arrow). Additional MR images (not shown) demonstrated hematoma formation in medial region of breast. Histopathologic specimens (not shown) revealed small papilloma that was smaller than the MR imaging–detected mass. (d, e) Repeat MR images obtained 1 week later show persistence of enhancing mass (in d) adjacent to the hematoma (arrowhead). MR-guided needle localization and excisional biopsy (not shown) revealed 6-mm invasive tubular cancer.

 
These two cancers missed at core-needle biopsy represented 4% of all the cancers (n = 56) detected in this study population, which consisted of 52 cancers found at core-needle biopsy, two ADH lesions upgraded to DCIS, and two false-negative lesions.

Benign Histologic Findings
Thirteen lesions that were benign at core-needle biopsy and 7–56 mm (mean, 19.2 mm) in diameter at MR imaging were validated at subsequent excisional biopsy or mastectomy; at 6-month follow-up MR imaging, which revealed lesion resolution or decreased lesion size; and/or on the basis of improved clinical findings. The benign histologic findings are summarized in the Table.

Clip Placement
A clip was placed in 75 of the 85 cases. In the remaining 10 cases, a clip was not placed owing to technical failure (n = 3), patient refusal (n = 3), or physician choice (n = 4). In two of the three cases of technical failure, the clip and collagen pledget became lodged in the biopsy device and precluded a second attempt. In the third case, the clip appeared to be deployed; however, at repeat MR imaging, the biopsy site and expected location of the clip were obscured by air in the biopsy cavity. At follow-up mammography, no clip was identified.


   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
References
 
Our experience with MR-guided biopsy performed by using the described vacuum-assisted core-needle biopsy system with a 9-gauge biopsy needle demonstrated the positive features of this system compared with the features of 14-gauge MR-compatible biopsy guns (18,19). First, although the procedural times were not prospectively recorded, prebiopsy imaging, the biopsy procedure itself, and postbiopsy care were performed within 30–60 minutes. The biopsy portion of the procedure—from placement of the introducer to sampling of the lesion—was very time efficient, so lesion visibility was minimally diminished. To the contrary, Kuhl et al (18), in a study of MR-guided core-needle biopsy performed by using various MR-compatible 14-gauge core-needle biopsy guns, reported that decreasing visibility of the target lesion that resulted from long biopsy times necessitated additional contrast material administration in 49 of 78 cases.

Second, in our study, minimal artifact was produced by the introducer, in contrast to experience with MR-compatible 14-gauge core-needle biopsy guns, with which needle artifact obscured lesions smaller than 1 cm (18). Third, accurate clip placement can be used to guide subsequent excisional biopsy. Accurate clip placement at MR imaging is important for two reasons: First, the entire enhancing lesion can be removed at MR-guided core-needle biopsy. (Clip placement allows accurate MR-guided wire localization of the biopsy site when residual enhancement and/or biopsy changes cannot be identified.) Second, most lesions in which biopsy was performed with MR guidance are not visible with mammography and US. (The clip can be localized with mammographic guidance when excisional biopsy is required.) Thus, accurate clip deployment is a critical component of MR-guided vacuum-assisted core-needle biopsy. Additional work is needed to improve the mechanism of clip deployment and increase clip conspicuity so that successful clip placement can be determined while the biopsy coil is still in place.

There is little published experience with histologically underestimated lesions sampled at MR-guided core-needle biopsy. Chen et al (19) reported underestimated lesions in two of five ADH cases when they used 14-gauge core-needle biopsy guns. In these two cases, invasive cancer was found at surgery. Liberman et al (17), using the 9-gauge Suros vacuum system, reported one case (4%) of histologic underestimation in which ADH was diagnosed at core-needle biopsy and DCIS was found at excisional biopsy. Perlet et al (16), using an 11-gauge vacuum system, reported three (of 17 [18%]) cases of histologic underestimation of ADH to DCIS. In our series, two (25%) of eight patients with ADH at core-needle biopsy had DCIS at excisional biopsy. In terms of histologically underestimated DCIS lesions, Chen et al (19) reported one case of DCIS at core-needle biopsy, and this case was upgraded to invasive cancer at surgery. Perlet et al (16) reported 47 cases of DCIS at core-needle biopsy, and none of these cases was upgraded to invasive cancer at surgery. Liberman et al (17) reported one case of DCIS at core-needle biopsy, and in this case, DCIS was confirmed at surgery. In our series, four (24%) of 17 DCIS lesions were underestimated: Core-needle biopsy yielded DCIS; however, both DCIS and small areas of invasive cancer were identified at subsequent surgery.

Although the numbers of cases in our series were small, the rate of lesion underestimation with 9–11-gauge vacuum-assisted core-needle biopsy appears to be lower than that with 14-gauge automated biopsy guns. Given the ongoing controversies regarding these high-risk lesions detected at core-needle biopsy, in our practice, we continue to recommend excisional biopsy when MR-guided core-needle biopsy yields a diagnosis of radial scar, lobular carcinoma in situ, or ADH.

Of the total 85 lesions evaluated in our study, two (2%) were false-negative (ie, benign non–high-risk lesion at core-needle biopsy with malignant diagnosis at subsequent surgery). The two cancers missed at core-needle biopsy represented 4% of all the cancers diagnosed in this study population. In both cases, the benign core-needle biopsy results were discordant with the MR imaging findings and subsequent MR-guided wire localization revealed invasive ductal cancer. In both of these false-negative cases, MR-guided core-needle biopsy was complicated—by bleeding in one case and by technical difficulty in placing the introducer in the second case. Also in both cases, lesion visibility was diminished such that biopsy changes within the lesion could not be documented: Visibility was obscured owing to bleeding in one case and owing to contrast material washout in the second case.

In the German multicenter trial of Perlet et al (16), seven (2%) of 334 biopsies were deemed to be unsuccessful. All seven procedures yielded false-negative findings, which were validated either immediately on postbiopsy MR images or with imaging-histologic comparison. Liberman et al (17) reported one (of 27 [4%]) false-negative case, in which fibrosis and fibroadenoma were found at core-needle biopsy and DCIS was found at surgery. Kuhl et al (18) also reported one (of 78 [1%]) false-negative case, in which a radial scar was found at core-needle biopsy and a radial scar with surrounding invasive cancer was found at surgery. The potential for false-negative results at MR-guided core-needle biopsy underscores the importance of careful radiologic-histopathologic correlation in each case to avoid any delays in diagnosis.

The true false-negative rate of MR-guided core-needle biopsy, which would include not only the immediately determined false-negative cases identified on the basis of histologic discordance but also the delayed false-negative cases, remains to be determined. In our series, as well as in series published to date, the reported false-negative rates were determined only for those cases in which surgical or MR imaging follow-up was performed (16,18). This was a limitation of our study. We reported on only those 85 lesions with findings that were validated with subsequent excisional biopsy or mastectomy or with short-term follow-up MR imaging that demonstrated a decrease or resolution of the initial MR imaging findings. Fifty-two (61%) of these 85 lesions were malignant at core-needle biopsy. This high percentage of malignant lesions is a result of the validations performed for all malignant and high-risk diagnoses, which were not performed for the majority of the benign diagnoses.

Determining the accuracy of MR-guided core-needle biopsy may not be as straightforward as determining the accuracy of mammographically and US-guided core-needle biopsies, for which there are well-established protocols for interpreting benign results. At present, there is no well-accepted follow-up imaging protocol to address the benign results of core-needle biopsy of lesions detected at MR imaging only. Because false-negative cases can occur and successful sampling of small lesions can be hindered by contrast material washout and biopsy-induced changes, it may be prudent to recommend 6-month follow-up MR imaging for all nonspecific benign core-needle biopsy results that are believed to be concordant with MR imaging findings. A specific benign diagnosis such as fibroadenoma, when concordant with MR imaging findings, may not require follow-up MR imaging. Long-term follow-up of patients with benign findings at MR-guided core-needle biopsy is needed to establish the false-negative rate of MR-guided core-needle biopsy so that both immediate and delayed false-negative cases can be identified.

It should be noted that a major disadvantage of MR-guided vacuum-assisted core-needle biopsy is its cost. Currently, the entire biopsy set, including the introducer kit and biopsy needle, are disposable. The total Medicare allowance for one MR-guided core-needle biopsy procedure is approximately $500. Additional investigation is needed to develop more cost-efficient systems. In addition, the cost of the needles will probably decrease as the use of them increases.

MR-guided vacuum-assisted core-needle biopsy appears to be a reasonable alternative to MR-guided wire localization for biopsy of suspicious lesions that are detected at MR imaging only and classified as Breast Imaging Reporting and Data System category 4 or 5 masses. We believe that additional clinical investigation to compare MR imaging findings with histopathologic and long-term follow-up results is needed to reduce the numbers of false-negative results and guide the development of an imaging follow-up protocol for benign results of biopsies of lesions detected at MR imaging only. We also believe that technical advances are needed to improve the success and accuracy of clip deployment and to develop more cost-efficient biopsy systems.


   FOOTNOTES
 

Abbreviations: ADH = atypical ductal hyperplasia • DCIS = ductal carcinoma in situ

Authors stated no financial relationship to disclose.

Author contributions: Guarantor of integrity of entire study, S.G.O.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; approval of final version of submitted manuscript, all authors; literature research, S.G.O.; clinical studies, all authors; and manuscript editing, S.G.O.


   References
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 

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