Diagnostic ultrasound ( PDFDrive )

808 PART III Small Parts, Carotid Artery, and Peripheral Vessel Sonography
C
M
M
1
A
B
FIG. 21.72 Lymph Node: Spectrum of Normal Appearances. (A) In young patients the mediastinum of the lymph node tends to be uniformly
hyperechoic because the medullary cords and sinuses ill the entire mediastinum (M). C represents the lymph node cortex. (B) In older patients
fatty iniltration of the lymph node may make the hypoechoic cortex very thin or barely visible (between the arrowhead and arrow).
speciically the metastases irst implant within the cortex.
Metastases that implant near the center of the cortical sinusoids
tend to widen the cortex focally and equally in inward and outward
directions (Fig. 21.73A). Metastases that implant in the subcapsular
sinusoids tend to bulge outwardly, creating a “mouse ear”
coniguration (Fig. 21.73B). Metastases that implant toward the
inner side of the cortical sinusoids tend to bulge into the lymph
node hilum, creating “rat bite” defects in the hilum (Fig. 21.73C).
When metastasis ills cortical sinusoids throughout the entire
lymph node, the cortical thickening becomes uniform, an appearance
that can be simulated by benign reactive lymph nodes (Fig.
21.73D). Metastases cause severe enough cortical thickening to
obliterate the hilum, which occurs more frequently than inlammation
(Fig. 21.73E). Lymph nodes that contain microcalciications
are metastatic until proven otherwise, especially when the
primary breast lesion manifests with microcalciications (Fig.
21.73F). Histologic sampling of the node should speciically target
the area of the cortex that is focally thickened.
Lymph nodes that demonstrate mild to moderate, symmetrical
cortical thickening of 3 mm or greater have a lower positive
predictive value for metastasis than those with clear-cut eccentric
cortical thickening, because they can be reactive or metastatic.
Comparison versus adjacent lymph nodes is the best way to
determine whether a lymph node with symmetrical cortical
thickening is a benign reactive node or a metastatic node. Unless
there is obvious evidence of inlammation in the ipsilateral breast
or upper extremity, reactive lymph nodes are usually reacting
to a systemic stimulus; thus all the lymph nodes will be reactive
(Fig. 21.74A). However, if the adjacent node is sonographically
normal, the node with symmetrical cortical thickening is more
likely to be metastatic (Fig. 21.74B). Assessment of adjacent
lymph nodes is not necessary when cortical thickening is so
severe that the hilum is completely obliterated, because this occurs
much more frequently in metastatic than reactive nodes (Fig.
21.74C). Although Doppler sonography can also be used to help
determine whether a node with symmetrical cortical thickening
is reactive or metastatic, gray-scale imaging of adjacent lymph
nodes usually makes this unnecessary.
Although diferences in morphology help determine whether
lymph nodes are abnormal, clear criteria for classifying these
changes have not been well established. Cortical thickness of
2.5 mm to 4 mm is used by some to diferentiate normal from
abnormal. Others use a cortex-to-hilum ratio; an increased
probability for malignancy is associated with a maximum cortical
thickness that is greater than the hilar thickness. 85-88
Abnormal axillary lymph nodes are located most commonly
within level 1 of the axilla, located lateral and inferior to the
lateral edge of the pectoralis minor muscle. hese are the irst
nodes involved by metastases, except in rare cases in which the
sentinel lymph node is a level 2 node. Lymph nodes deep to the
pectoralis minor muscle are level 2, and those that lie superior
and medial to the medial edge of the pectoralis minor muscle
are level 3, or infraclavicular, lymph nodes (Fig. 21.75). Rotter
lymph nodes lie between the pectoralis major and minor muscles
and lie anterior to and at the same level as level 2 lymph nodes
(Fig. 21.76). If undetected and untreated, they can give rise to
chest wall invasion. If level 3 nodes are positive, supraclavicular
and jugular lymph nodes should be assessed. Internal mammary
lymph nodes should be evaluated in all cases, but especially
when the primary lesion is medial and deep, and when bulky
axillary adenopathy may cause tumor damming and collateral
low medially (Fig. 21.77). Presence of metastasis to internal
mammary lymph nodes is especially important to radiation
oncologists. here is controversy regarding whether to prophylactically
irradiate internal mammary lymph nodes when axillary
nodes are positive for malignancy. However, if there are known