Diagnostic ultrasound ( PDFDrive )

CHAPTER 21 The Breast 807
(Fig. 21.71C). he sensitivity of ultrasound for extracapsular
rupture will be enhanced if the sonographer can recognize the
entire spectrum of its sonographic appearances.
he presence of implants should not discourage necessary
ultrasound-guided procedures. With ultrasound guidance, an
angle of approach that is almost parallel to the surface of the
implant can be used. A large amount of local anesthetic can be
injected between the lesion and the implant to “hydrodissect”
the lesion away from the implant and create a safe working space.
It is important to remember that patients with implants are
subject to the same disease processes as patients without implants.
Most patients are satisied with their implants and experience
no implant-related problems. he major problem for the sonographer
is that the implants are distracting and a breast malignancy
can be missed. Consequently, it is important to evaluate breast
tissues overlying the implant before turning attention to the
implants.
Breast Cancer Staging
When a patient is diagnosed with breast cancer, additional imaging
may be performed to determine disease extent within the involved
breast, disease involvement in the contralateral breast, and
ipsilateral lymph node status. he most sensitive imaging study
available is breast MRI, which identiies additional sites of
malignancy in the ipsilateral breast in approximately 16% of
patients and in the contralateral breast in 3% to 4% of patients 73
that would not have been seen on routine mammography.
Ultrasound has been studied for evaluation of disease extent
and has been shown to identify many of these additional sites,
although not as many as breast MRI. 74-76 hat being said, some
institutions prefer ultrasound for breast cancer staging because
histologic sampling of additional abnormalities can occur near
simultaneously with the diagnostic evaluation. 77
However, ultrasound is commonly used for evaluating lymph
node status. Until recently, if invasive breast cancer was diagnosed,
the patient would proceed with a sentinel lymph node biopsy
of the ipsilateral axilla at the time of surgical excision to determine
lymph node involvement. If positive lymph nodes were discovered,
the patient would return for axillary dissection. To bypass this
two-step process, preoperative ultrasound of the axilla was
commonly performed to identify potentially involved lymph
nodes. Should abnormal nodes be identiied, histologic sampling
could be performed before surgery. If the nodes were positive,
then the patient could go straight to axillary dissection and
avoid irst having a sentinel node biopsy. If negative, the patient
would still proceed with sentinel node sampling because the
false-negative rate of axillary lymph node sampling is approximately
42%. 78
A recent clinical trial has changed this routine. he American
College of Surgeons Oncology Group Z0011 trial was a randomized,
prospective study that compared survival and locoregional
recurrence rates ater sentinel node biopsy versus complete axillary
dissection in women with clinical stage T1 or T2, N0, M0 breast
cancer who were found to have one or two positive sentinel
nodes at the time of lumpectomy. 79,80 he study revealed no
signiicant diference between the two groups. Because of these
indings, the role of preoperative ultrasound evaluation of the
axilla is changing. Identifying lymph node metastasis preoperatively
in patients who would otherwise meet the Z0011 criteria
may no longer be necessary, because these patients may no longer
proceed with axillary dissection. Consequently, some institutions
no longer image the axilla at all, unless clinically relevant. Other
institutions still image the axilla preoperatively but reserve
histologic sampling for those patients in whom preoperative
identiication would change surgical management. Some studies
suggest that preoperative lymph node sampling revealing malignant
involvement is strongly correlated with tumor burden and
the number of involved nodes. 81,82 herefore some institutions
are continuing to perform preoperative lymph node sampling
and opting to proceed directly to axillary dissection in patients
with positive results, even if they would otherwise quality
for Z0011.
It is important to note, however, that the Z0011 results do
not pertain to patients with stage 3 tumors, more than two positive
sentinel nodes, or clinically positive axillary nodes or patients
undergoing mastectomy, neoadjuvant chemotherapy, or partialbreast
irradiation. 83 Ultrasound still plays a pivotal role in evaluating
the axilla in these patients.
Ultrasound can easily evaluate the lymph node basins involved
in breast cancer metastasis including axillary, internal mammary,
and supraclavicular. Normal lymph nodes have a sonographic
appearance similar to miniature kidneys. hey are oval in the
long axis, C-shaped in the short axis, and lat in the AP dimension
(Fig. 21.72A). he cortex of the lymph node includes the marginal
sinus, lymphoid follicles, and paracortex and is hypoechoic on
ultrasound, whereas the hilum of the lymph node includes
multiple blood vessels, fat, and the central sinus, which is
hyperechoic on ultrasound. 84 As patients age, fatty iniltration
of the lymph node may make the hypoechoic cortex very thin
or barely visible (Fig. 21.72B). he low of lymph passes through
aferent lymphatic channels, which enter the lymph node from
the periphery. he lymph then passes, in order, through the
subcapsular sinusoids, cortical sinusoids, medullary sinusoids,
and then out the eferent lymphatics, which exit through
the hilum.
Many gray-scale criteria have evolved for evaluating lymph
nodes, including size, shape, and echogenicity. Minimum
diameters greater than 1 cm are considered abnormal. However,
we have oten seen morphologically abnormal metastatic lymph
nodes with diameters less than 1 cm and normal atrophic lymph
nodes with diameters well over 1 cm. hus size is a poor criterion
for metastasis. Metastatic lymph nodes tend to become abnormally
round, but unfortunately this is a late inding. he cortex
in some (not all) metastatic lymph nodes becomes abnormally
hypoechoic. his inding may not be detected when using
harmonics because harmonics routinely make the cortex appear
more hypoechoic.
Morphologic assessment of the lymph node is more efective
than evaluating its size, shape, and echogenicity. Lymph nodes
that demonstrate eccentric cortical thickening should be
considered suspicious for metastasis. Given that the lymphatics
enter the node from the periphery, metastases initially implant
within the subcapsular or cortical sinusoids, causing focal cortical
thickening. he pattern of thickening depends on where