Directional Vacuum-assisted Biopsy Research Articles

Recognizing pitfalls in early and late migration of clip markers after imaging-guided directional vacuum-assisted biopsy.

Directional vacuum-assisted biopsy has become an irreplaceable tool in the management of suspicious mammographic lesions. Often, the entire lesion is removed and clips are used to localize the biopsy site. Postbiopsy mammograms are used to determine the adequacy of clip placement and the location of the clip. Clip displacement from the site of deployment is not an uncommon finding. Clips may migrate within the same quadrant where the lesion was located or to another quadrant of the breast. Clip migration may occur immediately after biopsy or may be seen on later follow-up mammograms. Clip migration can affect interpretation of mammographic findings and localization for future surgery. It should not be assumed that the clip is correctly located at the biopsy site on subsequent mammograms. It is essential to recognize the relationship of the clip to the targeted lesion to ensure accurate localization of lesions that require surgical excision.

Magnetic resonance imaging of the metal clip in a breast: safety and its availability as a negative marker.

This study assesses magnetic resonance (MR) safety of the stainless-steel clip inserted after stereotactic-guided directional vacuum-assisted biopsy (DVAB) of the breast, and evaluates its imaging value. We used a sausage as a substitute breast and inserted the clip into it. The MR images of the substitute were scanned using a breast coil, and it was then dissected. After the substitute experimentation, MR scanning of the breast was performed using a dynamic contrast enhanced technique, in which a clip was placed after DVAB for suspicion of ductal carcinoma was seen as grouped amorphous calcifications on mammography. On every magnetic resonance image of the substitute, the clip was seen as a spotty signal void, with no surrounding artifact. There was no movement and no evidence of increased clip temperature on dissected of the substitute, confirming the safety of breast MR with a clip in place. There was no patient complaint of feeling heat or pain during the MRI examination and there were only biopsy scars on the surgically excised breast specimen material. On the breast MR images, a spreading region of the tumor adjoining the position of the signal void was identified as an early enhancing lesion. The safety and reliability of breast MR examination using a mammotome clip was demonstrated by both the mock examination and the breast examination. It is possible to localize of tumor spread regions based on the marker position using the clip as a negative signal marker.

Stereotactic and ultrasound-guided breast biopsy.

Percutaneous imaging-guided needle biopsy has increasingly become an alternative to surgical biopsy for the histologic assessment of breast lesions. Percutaneous biopsy is faster, less invasive, and less expensive than surgical biopsy. Tissue acquisition is performed with automated core needles or directional vacuum-assisted biopsy probes. Guidance for percutaneous biopsy is usually provided by stereotaxis, ultrasound, and, more recently, under the guidance of MR imaging. Imaging guidance depends on lesion type and the results of diagnostic imaging studies. This article reviews indications, advantages, limitations, and controversial issues in percutaneous imaging-guided biopsy of breast lesions under stereotactic and ultrasound guidance. The potential for new research opportunities and directions is also discussed.

Single-step ultrasound localization of breast lesions and lumpectomy procedure

Background This review was made to evaluate whether the efficiencies of intraoperative ultrasound-guided localization could be extended to stereotactic biopsy cases by using a marker visible by sonography and mammography. Methods A retrospective review identified 170 stereotactic directional vacuum-assisted biopsy (DVAB) procedures marked with an ultrasound-visible marker. Localization device, imaging method, lesion retrieval, and margin status were assessed for patients having subsequent lumpectomy or wider excision. Results Nineteen of 170 patients underwent lumpectomies (12) or wider excision (7) localized by a radiofrequency device or 18G needle up to 7 weeks after stereotactic biopsy. In 15 of 19 procedures, an ultrasound-guided localization was performed intraoperatively, targeting the marker. All targeted lesions were successfully excised. In the 13 malignant lesions (of 19 surgeries), only 1 had a positive margin (8%). Conclusions Marking stereotactic biopsies with a sonographically visible marker allows ultrasound-guided intraoperative localization, improving efficiencies for the patient, surgeon, and operating room schedule.

Benign breast lesions: minimally invasive vacuum-assisted biopsy with 11-gauge needles patient acceptance and effect on follow-up imaging findings.

To evaluate patient acceptance of stereotactic or ultrasonographically (US) guided directional vacuum-assisted 11-gauge needle biopsy of breast lesions and short- and long-term changes at mammography and US resulting from the procedure. For 91 benign lesions that had been sampled at either stereotactic or US-guided directional vacuum-assisted breast biopsy performed with 11-gauge needles, clinical, mammographic, and US changes were evaluated 1 week after biopsy; 6-month follow-up findings were available for 74 lesions. The subjective outcome of the procedure and patient satisfaction were assessed on the basis of a patient-completed questionnaire that incorporated a multistage scoring system. Statistical analysis of scores for condition for both biopsy methods was performed with the chi2 test. Adverse events occurred during the procedure in four patients. Clinically visible hematomas were observed at 1-week follow-up in 79% of patients. Densities were observed on mammograms in 46% of patients 1 week after biopsy; hematomas with a maximum diameter of 2 cm were seen on sonograms in 74%. Six months after biopsy, mammography revealed discrete architectural changes in one case. No abnormalities were found at 6-month follow-up US. Fifteen patients had various complaints during the procedure; six reported feeling constrained during the first few days after biopsy, and one patient was not satisfied with the cosmetic result. No patient reported a retrospective preference for surgical biopsy instead of directional vacuum-assisted biopsy. Analysis of scores for the stereotactic and US-guided methods revealed a significant difference (P <.001) in favor of the stereotactic method for condition during biopsy, while scores for condition in the first days after biopsy were more equally distributed between the two methods (P =.386). Directional vacuum-assisted 11-gauge needle biopsy of the breast is well accepted by patients and rarely produces changes that may alter the mammographic or sonographic appearance of the breast at 6-month follow-up.

Granular Cell Tumor: A Benign Mimicker of Breast Carcinoma

Granular cell tumor is an uncommon benign neoplasm that, on rare occasions, presents as a breast mass. The diagnosis of this lesion can be challenging since it can mimic invasive breast carcinoma on clinical, imaging, and gross pathologic examination. Extensive surgery can be avoided by obtaining a preoperative histologic diagnosis by percutaneous core biopsy or directional vacuum-assisted biopsy with sonographic or mammographic guidance.

Atypical Ductal Hyperplasia Diagnosis by Directional Vacuum-Assisted Stereotactic Biopsy of Breast Microcalcifications

In 824 patients who underwent directional vacuum-assisted biopsies (DVABs) of breast microcalcifications, 61 (7.4%) showed atypical ductal hyperplasia (ADH). The 42 who subsequently underwent excision were the subjects of this study. Cases were evaluated for the mammographic characteristics of the lesion, the percentage of lesion removed according to mammography, and histologic findings (including number of large ducts and/or terminal duct–lobular units involved with ADH) in DVAB specimens. Pathologic findings in the surgical specimens in the area of the biopsy site also were recorded. In the DVAB specimens, ADH was confined to an average of 1.5 large ducts or lobular units and was associated with microcalcifications in all of the patients. Surgical specimens showed ADH in 15 cases, no residual lesion in 24 cases, and ductal carcinoma in situ in 3 cases. We found that microcalcifications that contain ADH in less than 3 lobules or ducts and/or that are removed completely by DVAB do not reveal higher-risk lesions on excision; thus, removal is unnecessary. When assessing microcalcifications with ADH, clinicians should consider the percentage of microcalcifications removed by DVAB and the extent of lobular involvement to better assess the need for excision.

Atypical ductal hyperplasia diagnosis by directional vacuum-assisted stereotactic biopsy of breast microcalcifications. Considerations for surgical excision.

In 824 patients who underwent directional vacuum-assisted biopsies (DVABs) of breast microcalcifications, 61 (7.4%) showed atypical ductal hyperplasia (ADH). The 42 who subsequently underwent excision were the subjects of this study. Cases were evaluated for the mammographic characteristics of the lesion, the percentage of lesion removed according to mammography, and histologic findings (including number of large ducts and/or terminal duct-lobular units involved with ADH) in DVAB specimens. Pathologic findings in the surgical specimens in the area of the biopsy site also were recorded. In the DVAB specimens, ADH was confined to an average of 1.5 large ducts or lobular units and was associated with microcalcifications in all of the patients. Surgical specimens showed ADH in 15 cases, no residual lesion in 24 cases, and ductal carcinoma in situ in 3 cases. We found that microcalcifications that contain ADH in less than 3 lobules or ducts and/or that are removed completely by DVAB do not reveal higher-risk lesions on excision; thus, removal is unnecessary. When assessing microcalcifications with ADH, clinicians should consider the percentage of microcalcifications removed by DVAB and the extent of lobular involvement to better assess the need for excision.

Atypical ductal hyperplasia of the breast diagnosed by 11-gauge directional vacuum-assisted biopsy

BackgroundSmall nonpalpable mammographic abnormalities are frequently diagnosed by percutaneous stereotactically guided core needle biopsy. The reliability of the histologic diagnosis of atypical ductal hyperplasia (ADH) made from tissue obtained by 11-gauge directional, vacuum-assisted biopsy of these nonpalpable breast lesions is unknown. MethodsThe records of 31 patients who were found to have ADH by 11-gauge directional vacuum-assisted biopsy were reviewed. All of these patients subsequently underwent surgical excision with needle localization biopsy of the ADH and they are the subjects of this retrospective study. ResultsEleven of the 31 patients with ADH on 11-gauge directional vacuum-assisted biopsy were upgraded to ductal carcinoma in situ or infiltrating carcinoma by the excisional biopsy. This was a 35% underestimation of malignancy in our patients. ConclusionsWhen the histologic diagnosis of ADH is made from tissue harvested by an 11-gauge directional vacuum assisted biopsy, surgical excision of the entire abnormality is recommended to avoid underdiagnosis of breast cancer.

Stereotactic breast biopsy with an 8-gauge, directional, vacuum-assisted probe: initial experience.

This study was prospectively conducted to assess the feasibility, safety and accuracy of an 8-G directional vacuum-assisted biopsy (DVAB) probe in the diagnostic management of nonpalpable breast lesions (NPBL). Of 170 planned procedures which were indicated for investigation of BI-RADS category-3 to category-5 lesions, 153 were performed in 138 consecutive patients. The probe was targeted by the stereotactic unit of a prone table (United States Surgical Corporation, Norwalk, Conn.; and Lorad, Danbury, Conn.). Four to 18 (mean 8) core specimens were obtained for each lesion. In case of complete removal of the lesion, a localizing clip was deployed at the biopsy site. Adequate material for histopathologic examination was obtained in all cases (100%). Four of 138 (3%) patients experienced mild hematomas. We observed 15 of 39 failures (38%) to place the localizing clips. Thirteen of 153 (8%) procedures were inconclusive and required reintervention. Following DVAB, 42 of 138 (30%) patients underwent surgery. Subject to incomplete follow-up of the entire cohort, we observed no false-positive and one false-negative diagnosis. These preliminary results suggest that DVAB using an 8-G probe are feasible, safe and accurate. In our experience, clip placement was problematic. It is probable that increasing the dimensions of DVAB will only be relevant in a limited number of clinical situations, primarily the desire to obtain complete radiologic resections of the target abnormality.

Sonographically guided directional vacuum-assisted breast biopsy: preliminary experience in Venezuela.

The purpose of this study was to evaluate the use of sonographically guided directional vacuum-assisted biopsy in the histologic diagnosis of breast lesions. Eighty-eight lesions in 83 women underwent sonographically guided 11-gauge directional vacuum-assisted breast biopsy during a 26-month period. Biopsies were performed using high-resolution sonography equipment with a 7.5-MHz transducer, obtaining a median of 17 specimens per lesion. Imaging studies, medical records, and histologic findings were reviewed. Median patient age was 48 years (range, 25-78 years). Median lesion size was 1.2 cm (range, 0.4-2.5 cm). Twenty-four (27.3%) of 88 lesions were palpable. The median time required to perform biopsy was 17 min (range, 10-40 min). Complete removal of the lesion seen at sonography occurred in 78 (88.6%) of 88 lesions and was significantly more frequent in lesions measuring 1.5 cm or less than in larger lesions (68/71 = 95.8% vs 10/17 = 58.8%,p < 0.0003). A surgical procedure was spared in 79 (95.2%) of 83 women. In 36 lesions with imaging and clinical follow-up after sonographically guided biopsy with benign findings (range, 4-24 months; median, 11.3 months), we found no evidence of cancer or scarring in the breast. In our small series, sonographically guided directional vacuum-assisted biopsy was a fast and accurate method for breast diagnosis. This technique resulted in complete removal of 95.8% of lesions shown at sonography measuring 1.5 cm or less and spared a surgical procedure in 95.2% of women. Further work is necessary to refine indications, evaluate cost-effectiveness, and assess long-term outcome.

Papillary lesions of the breast: evaluation with stereotactic directional vacuum-assisted biopsy.

To evaluate the use of stereotactic directional vacuum-assisted biopsy (SDVAB) in diagnosing and managing papillary lesions of the breast. The authors retrospectively reviewed the mammographic and histopathologic findings of 26 cases in which papillary lesions were diagnosed at SDVAB. In all cases, subsequent surgical excision (n = 20) or long-term imaging follow-up (n = 6) was performed and correlated with findings at SDVAB. SDVAB of 26 lesions yielded tissue that was classified as benign in 12, atypical in six, and malignant in eight. Of the 12 lesions that were diagnosed as histologically benign at SDVAB, six were surgically excised. Of these six lesions, five yielded benign correlative results. The sixth lesion was thought to be discordant with the imaging findings, and was surgically excised and determined to be malignant. Of the six benign lesions that were not surgically sampled for biopsy, five decreased in size and one was not seen at radiographic follow-up. Of the six lesions diagnosed as atypical at SDVAB that were surgically excised, one was benign and five were atypical. None proved to be malignant. Of the eight lesions diagnosed as malignant at SDVAB, surgical excision demonstrated ductal carcinoma in situ in all eight; two also had foci of invasive carcinoma. Benign and malignant papillary lesions of the breast can be reliably diagnosed at SDVAB when the SDVAB results correlate with the imaging findings. However, the extent of malignant papillary disease may be underestimated at SDVAB; in our study, invasive carcinoma was later discovered in 25% of patients with this diagnosis.

Sonographically guided directional vacuum-assisted breast biopsy using a handheld device.

The goal of this study was to show that one can safely remove all sonographic evidence of masses in the breast less than or equal to 1.5 cm in greatest dimension using the 11-gauge handheld Mammotome, thereby reducing the possibility of a false-negative diagnosis and other shortcomings of the automated core biopsy device. Over a 12-week period (May 3--July 31, 2000), 124 sonographically guided breast biopsies were performed in 113 patients, using a new handheld directional vacuum-assisted biopsy device. All lesions that were less than or equal to 1.5 cm were biopsied using a handheld Mammotome; an attempt was made to continue the biopsy until no sonographic evidence of the lesion remained. Of these 124 lesions, 14 had infiltrating ductal carcinomas, four had infiltrating ductal carcinomas with associated ductal carcinoma in situ, one had infiltrating lobular carcinoma, one had ductal carcinoma in situ, three had atypical ductal hyperplasias, one had atypical lobular hyperplasia, and one had phyllodes tumor. Only one infiltrating ductal carcinoma was entirely removed histologically at Mammotome biopsy. There were no underestimates of disease. No cases of epithelial displacement were observed in any of the surgical excisions of malignancies. The remaining 99 lesions were benign. The handheld Mammotome diminishes the shortcomings of the automated core biopsy device. It reduces the possibility of false-negatives and underestimation of disease. It eliminates the need for multiple insertions and reduces the likelihood of epithelial displacement. As a result, we now use this device for all sonographically guided biopsies of breast masses smaller than 1.5 cm and recommend that others consider it for such use.

Displacement of Microcalcifications during Stereotactic 11-gauge Directional Vacuum-assisted Biopsy with Marking Clip Placement: Case Report

A 53-year-old woman with right breast microcalcifications of intermediate concern underwent stereotactic directional vacuum-assisted biopsy with marking clip placement. Postbiopsy mammograms showed displacement of a few of the targeted microcalcifications adjacent to misplaced marker clips. Mammography following stereotactic breast biopsy is important to document the location and number of residual calcifications and to determine the adequacy and location of clip placement.

Stereotactic localization of breast lesions: how it works and methods to improve accuracy.

A computer simulation of stereotactic breast biopsy was developed that paralleled the geometric configuration of a currently available breast biopsy system. This model was developed to define and improve the targeting of breast lesions with stereotactic biopsy techniques. Lesions must be clearly identified and accurately targeted on both views for successful localization. Nonvisualization of a lesion may result from overlying tissue or from the geometric configuration of the imaging system. Familiarity with the geometric configuration of the biopsy unit, especially the location of the reference point and center of rotation, facilitates understanding of apparent changes in lesion position (parallax shift). Inaccuracy in lesion targeting on one or both views will manifest predominantly as an error in the calculated z value (depth). The magnitude and direction of this error are largely determined by the direction of the targeting error. Compensatory strategies include use of a long-throw core biopsy gun or directional vacuum-assisted biopsy device and additional sampling along the z axis and should be accompanied by critical evaluation of both pre- and postfire images. Understanding geometric considerations as well as how targeting accuracy affects accuracy in lesion localization should lead to greater success in sampling even challenging breast lesions at stereotactic biopsy.

Stereotactic breast biopsy of nonpalpable lesions: determinants of ductal carcinoma in situ underestimation rates.

To measure the effect of biopsy device, probe size, mammographic lesion type, lesion size, and number of samples obtained per lesion on the ductal carcinoma in situ (DCIS) underestimation rate. Nonpalpable breast lesions at 16 institutions received a histologic diagnosis of DCIS after 14-gauge automated large-core biopsy in 373 lesions and after 14- or 11-gauge directional vacuum-assisted biopsy in 953 lesions. The presence of histopathologic invasive carcinoma was noted at subsequent surgical biopsy. By performing the chi(2) test, independent significant DCIS underestimation rates by biopsy device were 20.4% (76 of 373) of lesions diagnosed at large-core biopsy and 11.2% (107 of 953) of lesions diagnosed at vacuum-assisted biopsy (P <.001); by lesion type, 24.3% (35 of 144) of masses and 12.5% (148 of 1,182) of microcalcifications (P <.001); and by number of specimens per lesion, 17.5% (88 of 502) with 10 or fewer specimens and 11.5% (92 of 799) with greater than 10 (P <.02). DCIS underestimations increased with lesion size. DCIS underestimations were 1.9 times more frequent with masses than with calcifications, 1.8 times more frequent with large-core biopsy than with vacuum-assisted biopsy, and 1.5 times more frequent with 10 or fewer specimens per lesion than with more than 10 specimens per lesion.

Atypical Ductal Hyperplasia and Ductal Carcinoma In Situ as Revealed by Large-Core Needle Breast Biopsy

This investigation compares the frequency of histologic underestimation of breast carcinoma that occurs when a large-core needle biopsy reveals atypical ductal hyperplasia or ductal carcinoma in situ with the automated 14-gauge needle, the 14-gauge directional vacuum-assisted biopsy device, and the 11-gauge directional vacuum-assisted biopsy device. Evaluation of 428 large-core needle biopsies yielding atypical ductal hyperplasia (139 lesions) or ductal carcinoma in situ (289 lesions) was performed. The results of subsequent surgical excision were retrospectively compared with the needle biopsy results. For lesions initially diagnosed as ductal carcinoma in situ, underestimation of invasive ductal carcinoma was significantly less frequent using the 11-gauge directional vacuum-assisted biopsy device when compared with the automated 14-gauge needle (10% versus 21%, p < 0.05) but was not significantly less frequent when compared with the 14-gauge directional vacuum-assisted device (10% versus 17%, p > 0.1). For lesions diagnosed initially as atypical ductal hyperplasia, underestimation of ductal carcinoma in situ and invasive ductal carcinoma was significantly less frequent using the 11-gauge directional vacuum-assisted biopsy device compared with the 14-gauge directional vacuum-assisted device (19% versus 39%, p = 0. 025) and with the automated 14-gauge needle (19% versus 44%, p = 0. 01). The frequency of histologic underestimation of breast carcinoma in lesions initially diagnosed as atypical ductal hyperplasia or ductal carcinoma in situ using large-core needle biopsy is substantially lower with the 11-gauge directional vacuum-assisted device than with the automated 14-gauge needle and with the 14-gauge directional vacuum-assisted device.

Cost-effectiveness of stereotactic 11-gauge directional vacuum-assisted breast biopsy.

The purpose of our study was to determine the frequency with which stereotactic 11-gauge directional vacuum-assisted breast biopsy obviated a surgical procedure and to calculate cost savings attributable to that biopsy method. We retrospectively reviewed 200 consecutive solitary nonpalpable lesions on which stereotactic 11-gauge directional vacuum-assisted breast biopsy was performed. Cost savings were calculated using Medicare reimbursements. Mammograms, histologic findings, and medical records were reviewed. Stereotactic 11-gauge directional vacuum-assisted biopsy obviated a surgical procedure in 151 (76%) of 200 lesions, including 112 (73%) of 154 calcific lesions and 39 (85%) of 46 masses. Reasons for not obviating a surgical procedure in 49 lesions (25%) included recommendation for surgical biopsy in 35 lesions (18%), small carcinomas treated by excision in 10 lesions (5%), and histologic underestimation in four lesions (2%). Stereotactic 11-gauge directional vacuum-assisted biopsy decreased the cost of diagnosis by S264 per case, a 20% ($264/$1289) decrease in the cost of diagnosis compared with surgical biopsy. Of 200 lesions that had stereotactic 11-gauge directional vacuum-assisted biopsy, 106 (53%) would not have been amenable to 14-gauge automated core biopsy because of their small size, their superficial location, or inadequate breast thickness. Stereotactic 11-gauge directional vacuum-assisted breast biopsy obviated a surgical procedure in 76% of lesions, yielding a 20% decrease in cost of diagnosis compared with surgical biopsy. Although savings per case are modest, 11-gauge directional vacuum-assisted biopsy expands the spectrum of lesions amenable to stereotactic biopsy, increasing cost savings in the population.

CLINICAL MANAGEMENT ISSUES IN PERCUTANEOUS CORE BREAST BIOPSY

Percutaneous imaging-guided core biopsy is a less invasive and less expensive alternative to surgical biopsy for the evaluation of breast lesions. Percutaneous core biopsy is most often used for evaluation of BI-RADS category 4 lesions, but may also be helpful in the evaluation of some BI-RADS category 5 lesions. Stereotactic guidance is particularly useful for calcifications; for masses that can be seen with ultrasound, ultrasound guidance may be preferable because of the absence of radiation and lower cost. The automated core biopsy needle is excellent for mass lesions, but directional vacuum-assisted biopsy is superior for calcifications. Directional vacuum-assisted biopsy may also be preferable for small lesions that may require placement of a localizing clip and lesions that are superficial or in thin breasts. The more expensive ABBI device has substantial limitations, and its role in percutaneous breast biopsy has not been demonstrated. Complete removal of the mammographic target can occur at percutaneous biopsy, and is a more frequent event when the larger tissue acquisition devices are used. Complete removal of the mammographic target does not ensure complete excision of the histologic process. Further investigation is necessary to determine in which lesions, if any, complete removal of the target is advantageous. Epithelial displacement can occur during all breast needling procedures, but may be less frequent at directional vacuum-assisted biopsy than at fine-needle aspiration or automated core biopsy. There is no evidence that displaced cells are of biologic significance, but displaced DCIS can mimic infiltrating carcinoma. The pathologist should be aware of the findings of epithelial displacement, to avoid misdiagnosing DCIS as infiltrating ductal carcinoma. Some lesions warrant repeat biopsy or surgical excision after percutaneous core biopsy. Repeat biopsy is warranted if histologic findings and imaging findings are discordant. Surgical excision is warranted for lesions yielding a percutaneous diagnosis of ADH or possible phyllodes tumor. Controversy exists regarding the need for surgical excision after percutaneous diagnosis of radial scar, papillary lesion, ALH, or LCIS. Follow-up is necessary if percutaneous biopsy yields benign findings concordant with imaging characteristics. Follow-up protocols vary, but all require substantial commitment of time and resources. We have an embarassment of riches for performing percutaneous core biopsy of the breast. It can be estimated that approximately 1 million breast biopsies will be performed this year to diagnose approximately 200,000 breast cancers. Percutaneous core biopsy may spare many of these women the need for a more deforming, invasive, and expensive surgical biopsy. Further work is necessary to optimize criteria for patient selection, develop and define the role of new technologies for tissue acquisition, refine protocols for management after percutaneous breast biopsy, and assess long-term outcome, so that more women can benefit from this minimally invasive approach to breast diagnosis.

Mammographic Abnormalities Caused by Percutaneous Stereotactic Biopsy of Histologically Benign Lesions Evident on Follow-Up Mammograms

The purpose of our study was to evaluate how often a mammographic abnormality thought to be produced by the biopsy procedure was evident on the initial follow-up mammogram after percutaneous biopsy of impalpable histologically benign lesions. We compared three stereotactic percutaneous biopsy methods. A mammographic density seen well only in the projection parallel to the biopsy needle tract was evident in 2% (5/226) of the lesions for which 11-gauge directional vacuum-assisted biopsy was used, 0% (0/96) of the lesions for which 14-gauge directional vacuum-assisted biopsy was used, and 0% (0/422) of the lesions for which 14-gauge automated large-core biopsy was used. No mammographic abnormalities assessed as BI-RADS categories 3, 4, or 5 (according to the American College of Radiology's Breast Imaging Reporting and Data System) and thought to be produced by the biopsy procedure were evident after any of the biopsy methods.