| MR-guided vacuum assisted (VAB) biopsy of the breast
MRI
of the breast is a very sensitive imaging
method for the detection of invasive breast carcinoma. Nevertheless it’s
specificity is limited. MR-guided biopsy allows to avoid surgical biopsy
in benign lesions and may allow to optimize a definitive therapy in case
of proofing malignancy. Especially
under guidance of MRI, VAB offers several advantages compared to
core-needle biopsy (CNB). Since, with the usually available magnets and
coils, biopsy has to be performed outside the bore, the procedure itself
cannot be monitored. Errors in targeting the lesion may occur due to
tissue shift caused by needle
insertion, by bleeding or by
the injection of local anaesthetic. In contrast to CNB, VAB allows the
acquisition of a larger tissue volume. This is resulting in the reduction
of sampling error, which is important
for the histopathologic diagnosis of small in situ malignancies or
borderline lesions. Furthermore tissue shift by bleeding is minimized due
to continuous suction and minor errors may be compensated by removing a
sufficiently large area of tissue (1.5-2 cm in diameter). Finally correct
biopsy can be proven by direct visualization of lesion removal on the
postinterventional images. The accuracy of MR-guided VAB was evaluated in an European multicenter
study, which was supported by the European Commission (Biomed-2-project
BMH 4-CT 98-3741) during a
period of three years. This
study shows that MR-VAB is a reliable method. When
performed diligently with a critical review of pre - and
post-interventional images including correlation with histology the
accuracy is at least comparable to the accuracy of MR-guided localization
followed by surgery. The success rate (96%) did not depend on the lesion
size. Overall, 52% of the lesions were smaller than
1 cm. Due to the
fact that representative biopsy can be proven by direct visualization of
lesion removal on the post-interventional images unsuccessful or uncertain
biopsy (4%) became obvious immediately on post-biopsy images. Our study
also showed the influence of hormonal changes on the contrast enhancement
of the breast: In about 12 % of lesions which had been referred to MR-VAB
the lesion could not be reproduced on the pre-interventional planning MRI,
obviously due to hormonal changes within the menstrual cycle or due to
hormone replacement therapy. Although
the procedure usually can be performed without problems, in some cases
(6%) the biopsy may not be possible due to limitation of needle-access or
to problems related to the patient (e.g. patient too large to fit into the
magnet with respect to the height of the biopsy coil, patient who cannot
lie still during the procedure) . Even though MR-VAB offers a new alternative for the work up of MR-detected lesions, a sensible selection of those indications where MRI may be useful remains important to limit the number of lesions which require further work up, and therefore lead to additional costs and unnecessary patient anxiety.
Bibliographical reference:
Claudia Perlet Department of Breast Imaging and Intervention; Radiology, Klinikum Rechts der Isar, Technical University Munich, Germany
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