乳房病灶之 MRI 導引細針定位與真空輔助切片
張允中
國立台灣大學醫學院附設醫院
國立台灣大學醫學院
影像醫學部
放射線科
MRI-guided Wire Localization and Vacuum-assisted Biopsy of Breast Lesions
Yeun-Chung Chang, MD, PhD
Department of Medical Imaging, National Taiwan University Hospital
Department of Radiology, National Taiwan University College of Medicine
Magnetic resonance imaging (MRI) of the breast is the imaging modality of
the highest sensitivity compared to mammography and ultrasound [1].
However, breast MR has lower specificity for malignancy than mammography
and ultrasound. Not infrequently, there is difficulty to decide whether enhancing
incidental lesions on MR can be ignored, followed up or biopsied. Patients with
MR assessment category 4 or 5 usually receive tissue diagnosis. Unfortunately,
a “probably benign” interpretation did not completely exclude malignancy. It
has been reported a 7-10% of women with “probably benign” lesions which
subsequently developed malignant disease in high risk population; of these
malignancies, more than half were DCIS and more than half were detected by
MR imaging only [2]. MRI-guided procedure using needle localization or core
biopsy has been used successfully for a definite diagnosis of these enhancing
lesions.
Compared with ultrasound-guided biopsy and mammographic needle
localization and biopsy, it usually takes more time for MR-guided procedure.
Dedicated or targeted breast ultrasound usually compensates the need of
MR-guided procedure. A second-look ultrasound can decrease the percentage
of MR-guided procedure which is much more expansive and not widely
available. A second-look or reevaluation ultrasound is usually performed
before the decision of MR-guided needle procedure. The likelihood of
carcinoma was significantly higher among lesions with a US correlate (43%
carcinoma) than lesions without a US correlate (14% carcinoma) [3 ].
Mammographically and ultrasound occult breast cancers which were not
uncommon need tissue diagnosis under MR-guided procedure [4,5]. In
addition, spatial registration or correlation is sometime difficult for identifying
the same lesion among different imaging modalities due to different positions
and degree of compression of the breast tissue. Certain characters of detected
lesions, such as microcalcifications, might not be possibly visible on ultrasound
and MRI.
The management guideline for enhancing incidental lesion detected on
breast MRI has been proposed [5, 6]. Tissue proof is usually suggested for
patients with lesion more suspicious on breast MRI, such as higher signal
intensity after contrast enhancement in early phase, wash-out kinetic,
speculated or irregular shape, ill defined margin, and inhomogeneous, rim or
ductal enhancement [5,6]. Lesions with lower MRI score may received MRI
follow up in short interval while lesion with higher scores should be considered
the feasibility MRI-guided needle localization or biopsy if they are occult to
mammography or ultrasound. The positive predictive value (PPV) of biopsy for
lesions identified at breast MRI significantly increased with increasing lesion
size. Biopsy is rarely necessary for lesions smaller than 5 mm because of their
low (3%) likelihood of cancer [7].
MRI-guided needle localization of breast lesions provides a confident
approach for suspicious lesions detected on only MRI which cannot be
biopsied under ultrasound or mammography guidance [4,8]. The technique of
MR-guided needle localization is easy and can be performed few hours before
surgical intervention. For those lesions visible on T2-weighted images,
contrast enhancement might not be necessary. Otherwise, contrast
enhancement MRI is essential for identifying the suspicious lesion. According
to our previous results, MRI-guided needle localization was successfully
performed for breast lesions with size ranging from 0.6 to 5.0cm (1.44 ± 1.29
cm). Most of the lesions were accessed via lateral approach. The majority of
lesions were proved benign (58.3%). The rest of them included 16.7%
malignant lesions with DCIS, 25% borderline or high risk lesions (lobular
carcinoma in situ, atypical lobular hyperplasia, atypical ductal hyperplasia). No
complications occurred during and immediately after the procedures. One
patient with previously diagnosed invasive lobular carcinoma received a
follow-up MRI which confirmed complete surgical resection of the targeted
lesion three months after MR-guided breast needle localization revealed focal
fibrocystic change. One of the malignant lesions displayed positive surgical
margin for malignancy because surgical biopsy was planned instead
MRI-guided breast biopsy is usually performed with coaxial system using
vacuum assisted device ranging from 10G to 14G [9-12]. MRI-guided
vacuum-assisted biopsy requires extensive dedicated technical equipment
which is not widely available. Potential problems and complications of
MR-guided needle technique include accordion effect of compressed breast,
decreased lesion enhancement or lesion disappearance in the procedure,
small breast size and posterior lesion location, retained wire fragments,
breakage of the wire tips, hematoma or bleeding, etc.
MRI-guided needle localization can assist surgical intervention and
MRI-guided core biopsy can change patient treatment by reducing
unnecessary surgical biopsy and enable one-step surgery. As the increasing
need of breast MRI for cancer staging and screening, more indetermined or
suspicious lesions will be found in our daily practice. MR-guided needle
procedure is increased according to clinical demands even after careful
correlation between breast MRI and conventional breast images.
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