Summary: This image-driven review discusses the many uses for
ultrasound at various stages in the diagnosis of breast cancer. These include
targeted ultrasound for a mammographic finding, targeted ultrasound for a
clinical finding, image guidance for biopsy and clip placement, “second look”
ultrasound after MRI, and preoperative localization for breast conservation
Dr. O’Connell is Director of Women’s Imaging and Associate
Professor, Clinical Imaging Sciences, University of Rochester Medical
Center, Rochester NY.
Ultrasound has multiple uses at various
stages in the diagnosis of breast cancer. These include targeted
ultrasound for a mammographic finding, targeted ultrasound for a
clinical finding, image guidance for biopsy and clip placement, “second
look” ultrasound after magnetic resonance imaging (MRI), and
preoperative localization for breast conservation surgery. Ultrasound
also has proven value inscreening for breast cancer, but for several
reasons discussed below, ultrasound screening has limited use and
acceptance at this time.
Screening ultrasound for breast cancer detection is not in widespread
use for several reasons. It is time consuming and highly
operator-dependent. It also produces a greater number of false-positive
results than mammography. This in turn leads to more biopsies and
thereby increased cost. This outcome was demonstrated in preliminary
results from the American College of Radiology ImagingNetwork (ACRIN)
6666 trial.1 This trial was designed to provide guidance for
women and their doctors on the role of screening ultrasound. It was a
multicenter trial with 21 teams in 3 countries. Whole-breast ultrasound
was performed on 2800 high-risk women who were followed for 3 years.
Preliminary results showed that 40 cancers were diagnosed, and 12 of
those were demonstrated by ultrasound alone. However, the false-positive
rate for combined mammographic and ultrasound imaging was 10.4%
compared with 4.4% for mammography alone.
Targeted diagnostic ultrasound
ultrasound, also known as targeted ultrasound, is commonly performed
for an abnormality detected on mammography, such as a mass or an
asymmetric density. Use of ultrasound in the evaluation of palpable and
nonpalpable masses is extremely valuable and also cost effective in the
management of BIRADS 3, 4 and 5 lesions. If palpable masses appear
benign, according to strict sonographic criteria and have no features
suggestive of malignancy, then they can be managed with short-interval
follow-up, rather than biopsy.2
The classic sonographic
characteristics of malignancy include orientation with respect to the
chest wall, shape, margin, echogenicity and acoustic transmission.
Malignant features include nonparallel orientation, “taller than wide”
dimensions, irregular shape or margin, hypoechoic internal echogenicity
and posterior acoustic shadowing (Figure 1).
It is also good
practice to evaluate the adjacent axilla when a highly suggestive BIRADS
5 lesion is detected and biopsied. If the axillary node is positive for
malignancy, this may avoid the need for sentinel-node biopsy and the
resulting risk of lymphedema of the arm. Abnormal lymph nodes may be
rounded rather than bean-shaped, have an asymmetrically thickened cortex
and exhibit indentations or obliteration of the hilum. They are not
necessarily enlarged (Figure 2).
ultrasound is also invaluable for palpable findings especially in the
setting of dense-breast parenchyma with subtleor nomammographic findings
(Figure 3). This situation may include the clinical finding of a
discrete mass or a less-specific “thickening.” The negative-predictive
value (NPV) of a combination of negative mammography and negative
ultrasound of a palpable finding is 99.8%3although another study showed a 5% incidence of cancer in patients with a clinical finding of thickening.4
a mammographic or ultrasound finding is considered suspicious enough to
warrant biopsy, i.e. a BIRADS 4 or 5 lesion, ultrasound is the
preferred method for image-guided biopsy (Figure 4).5 There are 3 reasons for biopsy under ultrasound rather than stereotactic guidance:
- Physically, ultrasound-guided biopsy is easier on the patient.
- Ultrasound allows direct visualization of the actual biopsy and clip placement.
- Ultrasound can also detect bleeding and monitor hematoma development immediately.
Ductal carcinoma in situ
Since most cases of ductal carcinoma in situ (DCIS) are detected due to
microcalcifications and only a small percentage manifest as soft-tissue
density without calcifications, ultrasound does not play a role in the
detection of DCIS. Stereotactic biopsy with specimen radiography is
preferred for biopsy of clustered calcifications.
“Second look” ultrasound
ultrasound is performed after breast MRI demonstrates an area of
enhancement which is occult to mammography (Figure 5).
is an example of a “targeted ultrasound,” directed at the area of MRI
enhancement. This approach includes BIRADS 0lesions requiring further
evaluation, BIRADS 3 lesions, for which short-interval follow-up is
indicated, and BIRADS 4 or 5 lesions requiring biopsy. Ultrasound-guided
biopsy is not only physically easier but is less costly and more
readily available for biopsies and follow-up than MRI and also does not
require contrast enhancement. Also, several areas can more easily be
biopsied at the same time. However, second-look ultrasound has
limitations. First of all, only about 25% of mammographically occult
lesions seen on MRI are detected on ultrasound. Also, since the MRI is
performed with the patient prone and the ultrasound is performed with
the patient supine, it is not always clear that a sonographic finding
correlates with a given MRI finding. However, a group in Toronto has
tested a method of sonographic coregistration using a prone ultrasound
table, which may become very useful in ultrasound evaluation and
correlation with MRI findings.6
wire localization (Figure 6) is the preferred method of management for
masses seen on ultrasound. The benefits of ultrasound vs. mammographic
- Direct visualization of the target lesion.
- Obtaining the shortest distance possible from skin to lesion.
- Making exact needle-length measurements.
- Visualization of the passage of the needle through the mass followed by wire deployment and needle removal.
for a subtle lesion that may not be visible on specimen radiography, a
tissue marker clip can be placed in the lesion at the time of
localization (Figure 6) for subsequent specimen radiography to confirm
Ultrasonographic strain imaging
is being evaluated for distinguishing between benign and solid masses.
This approach may reduce the number of benign biopsies, together with
their cost and morbidity; but according to Burnside et al.
“interobserver variability and image quality influence observer
performance.”7 There will no doubt be other technical advances and new applications for ultrasound in the breast.
ultrasound is highly operator-dependent and requires more physician
involvement, input and time than the other breast imaging modalities of
mammography and MRI. However, ultrasound has unique qualities that make
it indispensable and invaluable in the breast imaging armamentarium.
- Berg W, Blume J, Cormack J, et al. Combined screening
with ultrasound and mammography vs. mammography alone in women at
elevated risk of breast cancer. JAMA. 2008;299:2151-2163.
- Raza S, Chikarmane SA, Neilsen SS, et al. BI-RADS 3, 4, and 5 lesions: Value of US in management follow-up and outcome. Radiology. 2008;248: 773-781.
Soo M, Rosen EL, Baker JA, et al. Negative predictive value of
sonography with mammography in patients with palpable breast lesions. AJR. 2001; 177:1167-1170.
- Kaiser J, Helvie MA, Blacklaw RL, et al. Palpable breast thickening: Role of mammography and US in cancer detection. Radiology. 2002;223:839-844.
Mainiero MB, Gareen IF, Bird CE, et al. Preferential use of
sonographically guided biopsy to minimize patient discomfort and
procedure time in a percutaneous image-guided breast biopsy program.J Ultrasound Med. 2002;21:1221-1226.
Causer P, Piron CA, Jong RA, Plewes DB. Preliminary in vivo validation
of a dedicated breast MRI and sonographic coregistration imaging system.
- Burnside E, Hall TJ, Sommer AM, et al. Differentiating benign from malignant solid breast masses with US strain imaging. Radiology. 2007;245:401-410.