Diagnostic ultrasound ( PDFDrive )

810 PART III Small Parts, Carotid Artery, and Peripheral Vessel Sonography
FIG. 21.75 Metastases to Three Lymph Node Levels. Extended–
ield-of-view (FOV), obliquely oriented sonogram shows metastasis to
all three levels of axillary lymph nodes. Massive adenopathy and
microcalciications are seen in a level 1 lymph node that lies lateral and
inferior to the pectoralis minor muscle (dotted oval). A mildly enlarged
level 2 lymph node lies posterior to the pectoralis muscle. A moderately
enlarged level 3 lymph node with a microcalciication lies superior and
medial to the pectoralis muscle.
2
1
Level 1, 2, 3, AX LN’s OBL
Pec maj
R
Pec min
12 N 12 ARAD
Breast palp area per PT
2
Pec maj
Pec min
FIG. 21.76 Metastasis to Level 2 and Rotter Lymph Nodes. Rotter
lymph nodes (R) lie between the pectoralis minor and major muscles
at the same level as level 2 lymph nodes (2) and, if unrecognized, can
be a source for chest wall invasion. This patient has gross metastasis
that obliterates the mediastinum of level 2 and Rotter lymph nodes.
1
LO LT internal mamm chain
2
FIG. 21.77 Metastasis to Internal Mammary Lymph Nodes. Longaxis
extended–ield-of-view (FOV) image shows a gross internal mammary
lymph node metastasis (between arrows) lying between the irst (1)
and second (2) costal cartilages.
3
internal mammary nodal metastases, the radiation oncologist
will add an internal mammary ield to the treatment. Internal
mammary lymph node metastasis is most common in the irst
three interspaces just lateral to the sternum.
Sonographic–Magnetic Resonance
Imaging Correlation
he role of contrast-enhanced MRI for breast cancer screening
as well as diagnostic evaluation has expanded greatly in recent
years, along with the role of ultrasound correlation ater MRI.
Because of the high rate of false-positive results with contrastenhanced
breast MRI, treatment decisions require histologic
conirmation of the cause of abnormal enhancement. hus
image-guided biopsy of abnormal areas of enhancement is
necessary. However, MRI-guided biopsies can be costly, timeconsuming,
less readily accessible, and uncomfortable for the
patient. herefore patients are oten taken for second-look
ultrasound of the targeted area to see if the biopsy can be performed
with ultrasound instead. Second-look breast ultrasound
can be very efective at conirming the presence of additional
ipsilateral or contralateral foci of invasive breast cancer identiied
on MRI and targeting the inding for biopsy (Fig. 21.78). Similarly,
if a probably benign lesion seen on MRI has an ultrasound
correlate, this lesion can be followed with ultrasound instead of
MRI.
he challenge of second-look ultrasound examinations is
conirming that the inding seen on MRI truly correlates with
the ultrasound inding. Approximately 50% to 70% of lesions
seen on MRI can be found on second-look ultrasound. 89,90 Masses
are more easily identiied than nonmass enhancement. 89,90
Although it seems intuitive that larger masses would be more
easily visualized than smaller masses, this has not been consistently
shown in these studies. As a result, it is quite possible to perform
a second-look ultrasound and not ind an ultrasound correlate.
Alternatively, it is also possible to mistakenly correlate an
incidental ultrasound inding with the MRI target. If biopsy of
this area is then performed with ultrasound, there is the chance
of leaving the MRI target unsampled. herefore it is worthwhile
to pause before recommending a second-look ultrasound for
smaller, subtle areas of nonmass enhancement seen on MRI,
especially if one is suiciently concerned regarding malignancy
and believes that biopsy is warranted. It may be that MRI-guided
breast biopsy is the preferred approach for these patients.
If a second-look ultrasound examination is performed for a
suspicious MRI inding and identiies a correlate, there is a greater
chance that this MRI inding is malignant. 91 herefore it is worth
sampling. his raises the issue of pretest probability for diferent
types of ultrasound examinations. Breast ultrasound involves
three diferent patient groups, each with a diferent prevalence
of breast cancer (pretest probability): the screening group, the
diagnostic group, and the MRI correlation group. Diferent sets
of rules are needed for interpreting studies in these patients. In
the screening group the risk of cancer will be about 3 to 6 per
1000 patients (0.3%-0.6%). In the diagnostic group the risk will
be about 3% to 8%, and in the MRI correlation group the risk
is 30% to 60%. 89,90,92 In the screening group, we must deemphasize