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Case Report |
1 Women's Diagnostic Imaging Center, Swedish Cancer Institute, 1221 Madison St., Arnold Pavilion, Suite 520, Seattle, WA, 98104.
Received January 18, 2004;
accepted after revision April 3, 2004.
Address correspondence to J. Parikh.
Introduction
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Initial clip misplacement at the time of stereotactic breast biopsy is known to occur [3] and is typically identified immediately after the procedure. Three reports of migration of the MicroMark clip (Ethicon Endo-Surgery) within 5 weeks [4], 10 months [5], and 1 year [6] of accurate initial placement have been reported. Two cases of migration of the Gel Mark clip (SenoRx) within 8 days [7] and 10 weeks [4] of initial accurate placement have been reported [6]. To my knowledge, I am reporting the first case of Gel Mark clip migration, which occured within 15 days of initial accurate placement that was confirmed by mammographic imaging, that led to inaccurate preoperative needle localization, using digital stereotactic guidance.
Consultation with the institutional review board revealed neither their approval nor informed patient consent was required for this case report.
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Postprocedural craniocaudal images followed by mediolateral oblique mammographic images (Figs. 1A, 1B, 1C, 1D, 1E, 1F) confirmed removal of calcifications on biopsy with accurate initial clip placement at the biopsy site. An air-filled cavity and minimal hematoma changes were present after biopsy. Histology showed atypical ductal hyperplasia associated with microcalcifications in the core biopsy specimens. The patient was contacted 1 day after biopsy and reported no pain, bleeding, or swelling at the biopsy site. She was informed of the histologic results and surgical excision after preoperative needle localization was recommended.
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The patient returned 15 days after initial stereotactic biopsy for surgical excisional biopsy. Preoperative needle localization was done with digital stereotactic guidance with a modified disposable Kopans spring hook localization needle (Cook), using the same craniocaudal approach. The skin-entry site of the localizing needle was close to the scar from recent stereotactic breast biopsy. Postprocedural craniocaudal and true lateral mammographic images (Fig. 2) confirmed successful placement of the reinforced segment of the wire in close approximation to the clip. However, the clip had migrated 8 cm inferiorly, 1 cm laterally, and 1 cm posteriorly with respect to the initial biopsy site. The mammographic images, clip migration, and wire placement were all immediately discussed with the patient and breast surgeon.
After informed consent was obtained, the biopsy site was successfully localized stereotactically using a craniocaudal approach with a second modified disposable Kopans spring hook localization needle. Postprocedural craniocaudal and true lateral mammographic images (Fig. 3) confirmed successful placement of the reinforced segment of this second wire in close approximation to the hematoma at the biopsy site.
At surgery, the errant wire localizing the migrated clip was removed by the surgeon. A specimen containing the correctly placed wire containing the biopsy site was surgically excised. Histologically, the surgical biopsy specimen showed fibrosis, fat necrosis, hemorrhage, and chronic inflammation consistent with the previous biopsy site. No residual foci of atypical ductal hyperplasia were seen in the specimen, and microcalcifications were associated with benign adenosis. No intraductal or infiltrating malignancy was identified. The postoperative course was uneventful.
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TopIntroductionCase ReportDiscussionReferences |
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Initial clip misplacement at the time of stereotactic breast biopsy is usually identified immediately after the procedure. This initial clip misplacement typically ranges from a few millimeters to centimeters for the MicroMark clip and is largely attributed to the accordion effect along the z-axis during decompression of the breast after stereotactic biopsy [3]. Thus, initial clip misplacement is along the same axis as the needle trajectory. One letter [8] describes clip extrusion through the skin-entry site after stereotactic breast biopsy.
Delayed migration refers to shift of the marker location after initial correct placement of the marker into the biopsy cavity. Three reports of delayed migration of the MicroMark clip within 5 weeks [4], 10 months [5], and 1 year [6] of accurate initial placement have been reported. Two cases of migration of the Gel Mark clip within 8 days [7] and 10 weeks [4] of initial accurate placement have been recently reported. This article reports a third such migration of this clip that occurred within 15 days of initial accurate placement confirmed by mammographic imaging. To my knowledge, this is the first such migration that led to inaccurate preoperative needle localization.
The two previous reports of delayed migration of the Gel Mark clip have been along the axis of the insertion of the biopsy needle (i.e., the z-axis). This has been postulated to occur from the accordion effect. Initially at biopsy, the clip is within the biopsy cavity but does not adhere firmly to the breast tissue. When the breast is released from compression after stereotactic biopsy, movement of the clip from the biopsy site occurs along the trajectory of the biopsy needle, presumably the axis of least resistance.
The mechanism of delayed migration of the Gel Mark clip in the presented case is more complex. The migration of the Gel Mark clip in this patient was shown by mammography to be 8 cm inferiorly, 1 cm laterally, and 1 cm posteriorly. This movement in three dimensions (x, y, z) cannot be solely replaced by the accordion effect, which occurs along the z-axis. Some of this shift may be due to pliability of the breast and technical factors, such as slightly different angles of compression of the same projection during different mammograms. Minimal hematoma changes were noted at the stereotactic biopsy site on the immediate postbiopsy and preoperative mammogram images. Bleeding during or after the procedure may have contributed to shift of the clip. In addition, asymmetric resorption of the gelatin foam pledgets may have contributed to clip deviation.
In this case, delayed clip migration within 15 days of initial placement of the Gel Mark clip led to inaccurate initial preoperative stereotactic-guided needle localization. Based on this experience, as Philpotts et al. [6] recommend, I strongly recommend that repeat craniocaudal and lateral mammograms be obtained on the day of the needle localization before the procedure. This should be done irrespective of how soon after the biopsy the needle localization is scheduled. Unanticipated delayed clip migration can otherwise lead to inaccurate preoperative needle localization, dramatically affecting patient care.
Other methods can also be used to help assure accurate preoperative needle localization, even if there is delayed migration. If one is using digital stereotactic guidance with the same approach and equipment as the original stereotactic biopsy, the z-axis depth of the clip on the day of the localization can be compared with the z-axis depth of the lesion on the date of biopsy to determine significant z-axis migration. If mammographic-guided localization is done, the orthogonal view to the initial approach of biopsy enables comparison of the depths of the localizing needle, the clip, and the location of the lesion on the prebiopsy views. If sonogram guidance is used, the postbiopsy hematoma can be localized.
To summarize, a 60-year-old woman underwent 11-gauge vacuum-assisted stereotactic biopsy of a cluster of indeterminate calcifications in the right breast. Initial clip placement was confirmed by mammography to be at the biopsy site. The clip was localized for surgery stereotactically 15 days later, which confirmed interval migration of the clip in three dimensions. The delayed clip migration led to inaccurate preoperative needle localization. Based on this experience, radiologists are recommended to obtain orthogonal mammogram on the day of needle localization before wire placement, irrespective of the time interval after initial stereotactic-guided clip placement.
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