Dr. Ojeda-Fournier is an Assistant Professor of Clinical
Radiology at the Moores Cancer Center, University of California, San
Diego, La Jolla, CA; and Dr. Mahoney is a Professor of Radiology at the University of Cincinnati Medical Center, Cincinnati, OH.
work is based on educational exhibits presented at RSNA 2008 and ARRS
2009: Ojeda-Fournier H, Middleton MS, Comstock, CE. “MR-guided
BreastInterventions: Pearls and Pitfalls.”Radiological Society of North
America (RSNA) 2008 Annual Meeting, Chicago, IL. November 2008.
availability of MR-guided interventions is crucial to excluding breast
malignancy, especially with regard to lesions identified by breast MR
which are occult by other imaging modalities and physical examination.
Part 1 of a 2-part series, we discussed the techniques for performing
breast MR-guided core biopsy utilizing a grid system for lesion
In the second part of this series, we illustrate
and discuss the potential complications and some pitfalls related to the
procedure. In addition, we identify the useful pearls that can
potentially improve breast MRI biopsy outcome, including the importance
of radiology pathology correlations and determining concordance.
infection, and hematoma formation are potential complications of the
procedure. Patients are screened before an image-guided biopsy for
recent use of anticoagulants or aspirin products, and they are informed
of the associated increased risk for bleeding and hematoma formation.
After the procedure, direct digital pressure is applied to the biopsy
site for 10 minutes to promote hemostasis. The patients are advised to
refrain from heavy lifting and to wear a full support bra for the next
24 hours to help prevent delayed hematoma formation. Even with these
precautions, hematomas can occur after the procedure, as seen in Figure
1. Reassurance and time are the only treatments that have been provided
on the rare occasions in which a hematoma has been encountered. If the
hematoma is noted at imaging postbiopsy, using the vacuum-assisted
biopsy device to evacuate the hematoma, followed by direct digital
pressure, can be considered (Figure 2). Although recent reports in the
literature indicate that performing breast core biopsy in women on
anticoagulation is safe,1 biopsy is delayed if feasible until the effects of anticoagulation are reversed.
presence of hematoma and air in the biopsy cavity, as well as contrast
washout, limits postbiopsy imaging evaluation; assessment for complete
lesion removal may be nearly impossible. Evaluation of the marker clip
placement is not reliable, and taking time to plan and accurately
localize the lesion is of paramount importance. Once the biopsy is
performed, further lesion evaluation will be markedly limited.Figure 3
demonstrates the typical appearance of a postbiopsy cavity with hematoma
and gas present in the cavity.
Lesion location and body habitus
with stereotactic biopsy, posterior lesions can present a significant
challenge for MR-guided biopsy. Steps that can be taken in this
situation include oblique patient positioning and removing padding
material from the coil. This works well on laterally approached lesions
in patients with small to medium body habitus. Caution should be taken
in biopsy of posterior lesions because of proximity to the pectoralis
major muscle. Inadvertent sampling of the muscle is intensely painful
and can lead to marked hematoma formation. Carefully consider needle
localization if the lesion abuts or lies near the muscle. At minimum,
the trough of the biopsy device should be oriented away from the muscle.
medial lesion access is the most limited approach since the sternum bar
is lower than the lateral bar of the breast coil. In cases where the
lesion is located posteriorly and medially, a lateral approach may be
the only possible option. If the patient has a small body habitus,
performing a medial biopsy from the contralateral coil opening would be
feasible (Figure 4).
The challenges of posterior lesion biopsy are
illustrated in Figure 5. In this case the obturator is as far posterior
as possible for a lesion within the posterior medial breast. Note that
several centimeters of tissue are not accessible to biopsy because of
the sternal bar support.With vacuum-assisted directional sampling toward
the chest wall the lesion was successfully biopsied and yielded
papilloma. Directional sampling is not possible with spring-loaded
devices that need to traverse the lesion to obtain a proper sample.
Innovations in breast coils, including a sliding lateral grid, can help
access more posterior locations from both the lateral and medial
approach (Figure 6).
Similar to the limitations encountered with
stereotactic biopsy, the very thin breast can be challenging to biopsy.
Needle localization can be considered, keeping in mind the possibility
of an “accordion effect.” Minimizing compression, using a blunt-tip
biopsy needle (to decrease dead space), and infiltrating the tissue with
lidocaine are additional strategies to consider for biopsy of the thin
breast. An approach to the superficial lesion is to “puff up” the skin
tissue with lidocaine to gain greater lesion depth. The guide sheath can
also be used to protect the skin; however, care should be taken since
vacuum can be lost. A half-sample biopsy setting is available in certain
devices and allows for a decrease in the trough opening from 19 to 10
When introducing the
trocar, applying firm pressure to dissect through bands of dense tissue
and Cooper’s ligaments rather than displacing tissue is advantageous.
Tissue can be “snow-plowed,” as seen in Figure 7, and multiple imaging
checks may be required to ascertain that the tip of the needle is at the
appropriate depth, adding time to the procedure. One helpful procedure
is to insert the needle tip 1 cm past the expected location of the
lesion and then pull back to the calculated lesion depth to be certain
that the tissue has been properly dissected and not “snowplowed.”
the procedure to the patient and stressing that even small movement may
require repositioning of the biopsy needle and add time to the
procedure will often be sufficient to minimize patient motion.
Significant motion (>7- to 10-mm change in lesion location) may
require re-targeting. The obturator can be left in place and a new
trocar/obturator inserted in the newly targeted location (Figure 8).
Mammography technologists in the MR suite
a mammography technologist to the MR suite has been helpful and has
added efficiency to our practice. The mammography technologists are
experienced in setting up the breast biopsy equipment, positioning
patients, assisting during the procedure, and then performing a
postbiopsy mammogram for tissue marker check. The MR technologist can
then focus on imaging and maintaining a safe MR environment. The
greatest advantage to having the mammography technologist is the
continuity of care offered when going from the MR to the mammography
suite to perform the postbiopsy mammogram for tissue marker check.
Multiple and bilateral lesions
is no need to double bolus with contrast or to schedule patients for a
different day to perform multiple-site biopsies. Multiple or bilateral
lesions can be localized simultaneously and sequentially biopsied.
Multiple biopsies can be performed in one breast by inserting 2 or more
needles either from a medial or from a lateral approach or by inserting a
needle from the lateral and another from the medial approach (Figure
9). Bilateral lesions can be biopsied concurrently, but only from the
lateral approach (Figure 9). Care should be taken to label specimen
containers. For each site sampled, new biopsy probes should be used to
prevent cross-contamination of samples.
Lesion not seen at biopsy
a lesion is not identified at biopsy, additional delayed postcontrast
imaging is performed before considering aborting the procedure. If the
lesion is not identified after the additional delay, and this is
confirmed in both the axial-and sagittal-imaging planes, then a follow
up in 3 to 6 months is required to assess stability. As seen in Figure
10, menstrual effects and inflammatory changes can cause prominent foci
of enhancement. The patient in Figure 10 has undergone additional follow
up with no lesion identified at 6 months and 12 months. BI-RADS
category 3 is assigned to the study to ensure proper follow-up and to
avoid a delay in establishing potential cancer diagnosis. In a study by
Hefler et al,2 4 lesions initially not biopsied were
identified at short-term follow-up, and of these lesions, 3 proved
malignant. In Hefler’s study, strong compression was suspected as the
cause of limited enhancement at initial biopsy.
tracking of biopsy results and outcomes is an essential component of a
successful breast MR biopsy program. In an identical approach, as used
with stereotactic and ultrasound-guided breast biopsy, medical audit is
utilized in breast MR interventions. As per the Mammography Quality
Standards Act of 1999, biopsy results and tumor staging data are
collected and analyzed for breast MR-guided biopsy. In a recent study by
Han et al,3 a 29% cancer rate was found in women undergoing MR-guided breast biopsy. Eby and Lehman,4
in a summary of multiple published vacuum-assisted MR-guided biopsy
data, reported a 97% success rate in performing the biopsy, with an
overall 25% cancer yield.
Once pathology results are obtained,
correlation of pathology to imaging is performed and concordance is
determined. Figure 11 demonstrates one approach to establishing
concordance, in which the preprocedure image, the biopsy image, and the
pathology report are reviewed. This process is preferably done as a
group in order to obtain consensus. Histologic discordance was found in
7% of MR-guided biopsies of 342 lesions by Lee et al.5 For
those patients with benign histology, a 6-month follow-up is
recommended, similar to that recommended after stereotactic or
ultrasound core biopsy. Those with malignant, high-risk, or discordant
histology are referred to surgery.
breast MR has become an important adjunctive study in the evaluation of
the breast, but it lacks specificity to establish a definitive
diagnosis. Lesions identified by MRI that are occult to conventional
imaging modalities or physical examination may need to be further
evaluated with MR-guided tissue sampling. The techniques for MR-guided,
vacuum-assisted biopsy and the required imaging protocols have been
reviewed. Awareness of potential complications is important in the
performance of this procedure. Pitfalls, including limitations caused by
lesion location, motion, thin breasts, and the “snow-plow” phenomenon
have been illustrated. Multiple recommendationsand discussion of medical
audit and outcomes tracking were emphasized.
- Somerville P, Seifert PJ, Destounis SV, et al. Anticoagulation and bleeding risk after core needle biopsy. AJR Am J Roentgenol. 2008;191:1194-1197.
L, Casselman J, Amaya B, et al. Follow-up of breast lesions detected by
MRI not biopsied due to absent enhancement of contrast medium. Eur Radiol. 2003;13:344346.
- Han BK, Schnall MD, Orel SG, Rosen M. Outcome of MRI-guided breast biopsy. AJR Am J Roentgenol. 2008;191:1798-1804.
- Eby PR, Lehman CD. Magnetic resonance imaging-guided breast interventions. Top Magn Reson Imaging. 2008;19:151-162.
- Lee JM, Kaplan JB, Murray MP, et al. Imaging histologic discordance at MRI-guided 9-gauge vacuum-assisted breast biopsy. AJR Am J Roentgenol. 2007;189:852-859.