IMAGENOLOGIA EN CANCER DE TIROIDES

1. The Role of Sonography
in Thyroid Cancer
Stephanie F. Coquia, MD*, Linda C. Chu, MD, Ulrike M. Hamper, MD, MBA
KEYWORDS
Thyroid nodules Thyroid cancer Fine-needle aspiration biopsy
Cervical lymph node metastases Lateral neck compartment Central neck compartment
KEY POINTS
Thyroid nodules are commonly detected on ultrasound (US).
Specific sonographic features are found in many malignant nodules and lymph nodes.
Identification of cervical nodal metastasis is important for accurate staging and surgical manage-ment
of de novo thyroid cancer.
Pathologic diagnosis of a thyroid nodule requires fine-needle aspiration (FNA).
US accurately provides imaging guidance for FNA of indeterminate or suspicious thyroid nodules
and cervical lymph nodes.
US is routinely used in the postoperative surveillance of the neck for tumor recurrence in the thyroid
bed or nodal stations.
INTRODUCTION
According to the National Cancer Institute, an
estimated 63,000 cases of thyroid cancer will be
diagnosed in 2014.1 When pathologically well
differentiated and diagnosed early, the disease is
highly treatable and can be curable. The 5-year
relative survival rate of most types of stage I
thyroid cancer approaches 100%.2
US is used routinely in the diagnosis and man-agement
of thyroid cancer, from initial detection
and diagnosis to preoperative planning to post-operative
surveillance. This review discusses
the various roles of sonography in managing
patients with thyroid cancer and reviews the sono-graphic
appearance of thyroid cancer and nodal
metastases.
NORMAL ANATOMY AND IMAGING
TECHNIQUE
The thyroid gland is a bilobed gland that sits
atop the trachea within the anterior-inferior neck
(Fig. 1). The isthmus connects the right and left
thyroid lobes. Each lobe measures approximately
4 to 6 cm in length and less than 2 cm in width
and in the anterior-posterior dimension.3 The
normal isthmus measures less than 6 mm in the
anterior-posterior dimension. The normal gland is
homogeneous in echotexture and hyperechoic
compared with the adjacent strap muscles (see
Fig. 1).
After documentation of any thyroid lesion that
has suspicious features for primary thyroid cancer,
the cervical lymph nodes are imaged. A normal
lymph node has an elongated shape (a 2:1 ratio
between length and short-axis dimensions) and
demonstrates an echogenic fatty hilum. Vascular
flow is seen entering into the lymph node via the
fatty hilum (Fig. 2) and the cortex is symmetrically
hypoechoic.
The neck can be divided into nodal levels or
stations by anatomic landmarks. The numeric
classification system of the neck nodal stations is
outlined in Table 1 and depicted in Fig. 3.4 Using
this classification, the neck can be divided into
Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of
Medicine, 601 North Caroline Street, Baltimore, MD 21287, USA
* Corresponding author. 601 North Caroline Street, JHOC 3142, Baltimore, MD 21287.
E-mail address: scoquia1@jhmi.edu
Radiol Clin N Am - (2014) -–-
http://dx.doi.org/10.1016/j.rcl.2014.07.007
0033-8389/14/$ – see front matter 2014 Elsevier Inc. All rights reserved.
radiologic.theclinics.com

2. 2 Coquia et al
Fig. 1. Normal sonographic appearance of the thyroid.
The thyroid (arrows) sits atop the trachea (T) and is
a bilobed structure echogenic to the adjacent muscula-ture
(M).
central and lateral neck compartments. Stations I,
VI, and VII are considered central neck compart-ments
and stations II to V are considered lateral
neck compartments. The medial edge of the com-mon
carotid artery serves as a landmark to divide
the central from the lateral compartment. The
distinction between the central and lateral neck
compartments is important for the surgical man-agement
of thyroid cancer if nodal metastases
are present (discussed later).
IMAGING PROTOCOLS
Thyroid
The thyroid gland is imaged with a linear high-frequency
transducer (7–15 MHz). Occasionally,
if the thyroid gland is enlarged, a curved, lower-frequency
transducer may be used to fully image
the thyroid.
The right and left thyroid lobes are imaged in the
transverse and sagittal planes. Anterior-posterior
dimension, width, and length are measured at
the mid thyroid gland. The isthmus is measured
in the anterior-posterior dimension. Nodules, if
present, are measured in the transverse and
sagittal planes in three dimensions and evaluated
with color Doppler to document vascularity.
Cervical Lymph Nodes
The neck nodes are imaged with the same trans-ducers
as the thyroid: a high-frequency linear
transducer for most of the nodal stations and oc-casionally
a curved transducer for the lower and,
therefore, deeper level IV and VI lymph nodes.
Each nodal station within the neck is evaluated
to assess for the presence of normal or abnormal
lymph nodes. Normal-appearing lymph nodes
can be documented for each level, with the fatty
hilum included in the image. Measurement of
sonographically normal-appearing lymph nodes
is not necessary. Abnormal lymph nodes (dis-cussed
later) should be imaged and measured in
the transverse and sagittal planes. The nodes
also should be interrogated with color Doppler
US to assess for abnormal and disorganized blood
flow.
General imaging protocols for the thyroid gland
and cervical lymph nodes are summarized in
Table 2.
IMAGING FINDINGS AND PATHOLOGY
Types of Thyroid Cancer
There are several types of primary thyroid cancer.
Papillary thyroid carcinoma (PTC) is the most
common, accounting for approximately 75% to
80% of thyroid cancers. PTC is multifocal in
approximately 20% of cases and more common
in females than males. PTC usually presents
before age 40 years, often with cervical nodal me-tastases.
It is also the most common thyroid malig-nancy
in children. PTC has the best prognosis and
highest survival rate of all thyroid cancers, reach-ing
a 20-year survival rate of approximately 90%
to 95%. Other types of thyroid carcinoma include
follicular carcinoma (10%–20%), medullary carci-noma
(5%–10%), and anaplastic carcinoma
Fig. 2. Normal lymph nodes. (A) Lymph node with smooth, homogeneous, hypoechoic cortex (arrow), and central
echogenic fatty hilum. (B) Another lymph node demonstrating normal central hilar flow (arrow).

3. (1%–2%).5 Follicular thyroid carcinoma most often
affects women in the 6th decade of life and may
present with metastatic lesions to bone, brain,
lung, and liver via hematogenous spread. FNA
biopsy (FNAB) cannot differentiate between fol-licular
adenoma and carcinoma and surgical
resection is required to make this distinction. Med-ullary
thyroid carcinoma arises from the parafollic-ular
cells (C cells) of the thyroid gland. It is often
familial in origin (vs sporadic) and is associated
with multiple endocrine neoplasia type 2 syndrome
in 10% to 20% of cases. Patients present with
Table 1
Cervical nodal stations: numeric classification
Nodal Station Location
IA Submental lymph nodes
IB Submandibular lymph nodes
II Internal jugular vein chain from base of skull to the inferior border of the hyoid bone
A: Anterior to the internal jugular vein
B: Posterior the internal jugular vein
III Internal jugular vein chain from the inferior border of the hyoid bone to the inferior
border of the cricoid cartilage
IV Internal jugular vein chain from the inferior border of the cricoid cartilage to the
supraclavicular fossa
V Posterior triangle lymph nodes, posterior to the sternocleidomastoid muscle
A: From the skull base to the inferior border of the cricoid cartilage
B: From the inferior border of the cricoid cartilage to the clavicle
VI Central compartment nodes from the hyoid bone to the suprasternal notch
VII Central compartment nodes inferior to the suprasternal notch in the superior
mediastinum
Note: The lateral compartments (II–V) are separated from the central compartments (I, VI, and VII) by the medial edge of
the common carotid artery.
From Som PM, Curtin HD, Mancuso AA. An imaging-based classification for the cervical nodes designed as an adjunct to
recent clinically based nodal classifications. Arch Otolaryngol Head Neck Surg 1999;125(4):391; with permission.
Fig. 3. Diagram of the neck nodal stations. (From Som PM, Curtin HD, Mancuso AA. An imaging-based classifica-tion
for the cervical nodes designed as an adjunct to recent clinically based nodal classifications. Arch Otolaryngol
Head Neck Surg 1999;125(4):394; with permission.)
The Role of Sonography in Thyroid Cancer 3

4. elevated calcitonin levels due to the secretion of
calcitonin by the parafollicular cells. Anaplastic
thyroid carcinoma is the rarest and most aggres-sive
of the primary thyroid carcinomas, often fatal.
Its dismal prognosis carries a 5-year survival rate
of only 5%.6 There is often local invasion of the
adjacent soft tissues, trachea, and lymph nodes.
Risk factors for the development of thyroid
carcinoma include a history of neck irradiation
and a family history of thyroid cancer. Additional
risk factors that increase the probability of cancer
within a given thyroid nodule include age under
30 years or over 60 years and male gender.7 Nod-ules
greater than 2 cm also are reported to have
an increased risk of cancer (Fig. 4).8
Lymphomatous involvement of the thyroid is
rare, accounting for less than 5% of thyroid malig-nancies.
It may present as a manifestation of
generalized lymphoma or be primary to the thyroid
gland, usually a non-Hodgkin lymphoma. Hashi-moto
thyroiditis is a risk factor for the development
of thyroid lymphoma. Metastatic disease to the
thyroid is also uncommon; primary malignancies
include lung, breast, and renal cell carcinomas as
well as melanoma.6
Thyroid Nodules
Thyroid nodules are common in the United States;
it has been estimated that approximately 50%
of the adult population has thyroid nodules,
although less than 7% of these nodules prove ma-lignant.
6 US features suspicious for malignancy
are reviewed in this section. They are also summa-rized
in Table 3.
Calcification
Calcification within the thyroid may be classified
as microcalcification, coarse calcification, or peri-pheral
rim calcification. Although calcification may
be seen in both benign and malignant processes
of the thyroid, it is the US feature most commonly
associated with malignancy. Of these various
types, microcalcifications are the most specific
for thyroid malignancy, with a specificity of up to
95%.6 Microcalcifications are most commonly
found in PTC and appear as tiny punctate echo-genic
foci within the nodule (Fig. 5). Due to their
small size, they usually do not demonstrate poste-rior
acoustic shadowing. Colloid may also appear
on US as tiny echogenic foci but tends to appear
linear and demonstrates posterior ring-down or
comet-tail artifact (Fig. 6).9 Making this distinction
can be difficult, however, and biopsy should be
performed for indeterminate foci and for those
foci lacking the comet-tail artifact. Furthermore,
the presence of the ring-down artifact does
not necessarily preclude contemplating biopsy;
microcalcifications and colloid may coexist in the
same nodule.
Coarse calcification and peripheral rimlike
calcification may also be seen with thyroid malig-nancies;
however, they also may be found in multi-nodular
thyroids or goiters. Due to their larger size,
Table 2
Imaging protocols for thyroid and cervical
lymph node examinations
Thyroid imaging protocol
Transducer Linear 7–15 MHz (curved
lower-frequency
transducer as needed)
Gland
measurements
Lobes: anterior-posterior
dimension, width,
longitudinal dimension
Isthmus: anterior-posterior
dimension
Nodules Measurement of each
nodule in three
dimensions; color Doppler
interrogation of nodule
Cervical lymph node imaging protocol
Transducer Linear 7–15 MHz (curved
lower-frequency
transducer as needed)
Nodes Each nodal station
evaluated on each side of
the neck
Documentation of
abnormal lymph nodes:
Size measured in three
dimensions
Color Doppler
interrogation of node
Fig. 4. PTC. This nodule measured 5.2 cm and was
found in a 17-year-old girl who presented with neck
swelling. The patient’s age and the size of the nodule
increased the probability of this nodule being
malignant.
4 Coquia et al

5. these calcifications demonstrate posterior acous-tic
shadowing (Fig. 7). Coarse calcifications may
be seen in PTC; however, they are more com-monly
associated with medullary thyroid
carcinoma.6 Nodules with coarse calcifications
necessitate FNAB.
Solid hypoechoic nodule
Thyroid nodules may be completely cystic or solid
or a combination of both. Likewise, thyroid nodules
may be hyperechoic, isoechoic, or hypoechoic
to the remainder of the thyroid parenchyma. Most
PTCs are hypoechoic and nearly all medullary
thyroid carcinomas are hypoechoic.10 Some inves-tigators
believe the extremely hypoechoic nodule
The Role of Sonography in Thyroid Cancer 5
confers a higher risk of malignancy. Benign nodules
may also be hypoechoic; therefore, evaluation
for additional suspicious features, such as calcifi-cation,
should be performed. If no other suspicious
features are present, these hypoechoic nodules
can be biopsied when of sufficient size (discussed
later).
Follicular neoplasms (adenoma and carcinoma)
can also appear as solid, well-marginated, hypoe-choic
nodules with thin hypoechoic halos10 and
central linear hypoechoic striations or areas
(Fig. 8). Because the distinction between follicular
adenoma and carcinoma can only be made based
on vascular and capsular invasion, the diagnosis
can only be made by surgical resection. As such,
once a nodule is diagnosed as a follicular
neoplasm via FNAB, surgical management is the
next step.
Local invasion
Anaplastic thyroid carcinoma and thyroid lym-phoma
may present as large, rapidly growing
masses. The masses may be discrete or infiltra-tive.
Extracapsular extension into the soft tissues
is common with invasion into the trachea, neck
vessels, and strap muscles. There is usually asso-ciated
cervical lymphadenopathy.
Edge refraction shadow
Posterior acoustic shadowing from the edges of a
solid nodule has also been associated with PTC. It
is thought that the fibrotic reaction around the
edge of the tumor is responsible for the edge
refraction shadow.10
Other features suggesting malignancy in
thyroid nodules
Additional suspicious features include nodules
that are taller than they are wide,11 have irregular
shape or margins,11 demonstrate posterior acous-tic
shadowing in the absence of edge refraction, or
are accompanied by sonographically suspicious
lymph nodes, such as lymph nodes with
Table 3
Diagnostic criteria: sonographic features
suggestive of malignancy
US Feature Comment
Calcification Micro-, macro-,
coarse, peripheral
(especially micro)
Solid hypoechoic
nodule
Especially if very
hypoechoic
Local invasion More common in
anaplastic and
lymphoma
Edge refraction
shadow
Taller than wide Nodule anterior-posterior
dimension greater
than width
Irregular margins
Adjacent suspicious
lymph nodes
Size 2 cm
Posterior acoustic
shadowing
Fig. 5. (A, B) Examples of microcalcification. Multiple punctate echogenic foci (arrows) are seen within each of
the hypoechoic nodules. Both of these nodules are markedly hypoechoic with irregular borders. These nodules
were pathologically proved to be PTC.

6. calcification, cystic change, or abnormally in-creased
or disorganized blood flow. A more
detailed discussion of the sonographic findings
suspicious for cervical lymph node metastasis
from thyroid carcinoma follows.
Although these features can be seen in thyroid
malignancies, they are by no means pathogno-monic;
benign nodules may also demonstrate
these features. The differential diagnosis of thyroid
nodules is found in Table 4. Therefore, when nod-ules
present with features suspicious or sugges-tive
of malignancy, these should proceed to
biopsy when of sufficient size.
Size criteria for biopsy
Multiple guidelines for FNAB of thyroid nodules
exist because multiple medical specialties and
organizations are involved in the care of patients
with thyroid nodules. These include recommenda-tions
from the American Thyroid Association
(ATA), the Society of Radiologists in Ultrasound,
and the American Association of Clinical Endocri-nologists
(AACE).5,12,13 Regardless of the recom-mending
body, the guidelines take into account
the nodule’s sonographic appearance as well as
size. In addition, the ATA uses clinical risk stratifi-cation,
providing differing guidelines for high-risk
and low-risk patients. In general, for low-risk
patients, the various guidelines recommend
biopsy of solid nodules at sizes greater than 1 to
1.5 cm and mixed cystic and solid nodules at sizes
greater than 1.5 to 2 cm. The ATA decreases its
minimum size threshold to 5 mm in high-risk pa-tients
who have nodules with suspicious features
or nodules accompanied by suspicious lymph no-des,
whereas the AACE decreases its size
threshold below 1.0 cm if there are suspicious
sonographic features present.
Due to the multitude of guidelines available,
it may be confusing as to which specific recom-mendations
to follow. Each department or practice
should meet with the referring endocrinologists
and surgeons to decide which of the guidelines
is to be used by all members of the clinical team
to provide seamless care to patients.
Pitfalls of thyroid US in the detection of
nodules
Parathyroid adenomas may be confused with
thyroid nodules. Most parathyroid adenomas are
extrathyroidal in location; evaluation for the echo-genic
thyroid capsule separating the adenoma
from the thyroid tissue is helpful in making this
distinction. Parathyroid adenomas are usually
located posterior to the mid gland or inferior to
the thyroid gland (Fig. 9A). Adenomas are quite
vascular and obtain their vascular supply from
the thyroid (see Fig. 9B).
Fig. 6. Example of colloid within a predominately
cystic thyroid nodule. The punctate echogenic foci
demonstrate comet-tail artifact (arrow).
Fig. 7. Coarse calcification. Hypoechoic nodule
with slightly indistinct and irregular border demon-strates
a cluster of coarse echogenic calcifications
demonstrating posterior acoustic shadowing (arrow).
Pathology was PTC.
Fig. 8. Hypoechoic nodule. The nodule is well defined
and homogeneously hypoechoic with a thin hypoe-choic
halo. FNA resulted in pathology of follicular
neoplasm. The patient was scheduled for lobectomy
for definitive diagnosis.
6 Coquia et al

7. Hashimoto thyroiditis may also present with
nodules. The nodules are usually subcentimeter
in size (typically 2–3 mm and less than 6 mm)
and numerous (termed micronodulation or giraffe
pattern), however, causing diffuse heterogeneity
of the gland. This diffuse heterogeneity may
also create the appearance of larger nodules.
The borders of these apparent lesions are indis-tinct,
however. Moreover, because it is an auto-immune
process, prominent reactive cervical
lymph nodes, usually in level VI, may be present
and could be confused as suspicious lymph no-des.
These lymph nodes, however, usually have
fatty hila and maintain the morphologic appear-ance
of a benign lymph node. A truly discrete
nodule, however, in a patient with Hashimoto
thyroiditis should be viewed with concern
The Role of Sonography in Thyroid Cancer 7
because these patients are at increased risk for
both lymphoma and PTC.
Management of multiple thyroid nodules
Patients sometimes present with multiple nodules,
which may pose a dilemma regarding which nod-ules
to biopsy. Regardless of the number of nod-ules
present, the risk of thyroid cancer in a
patient is unchanged.5 Furthermore, it has been
found that although a majority of cancers found
in patients with multinodular thyroids are within
the dominant nodule, approximately one-third of
the cancers are found in the nondominant nodule.5
Therefore, each nodule should be evaluated inde-pendently,
evaluating for suspicious features and
then triaging the nodules for biopsy in the order
of most suspicious features and then by size.
Table 4
Differential diagnosis of thyroid nodules
Diagnosis Comment
Benign
Adenomatoid nodule
Follicular adenoma Surgical excision is required to differentiate adenoma from
carcinoma
Hashimoto thyroiditis Lymphocytic thyroiditis can be used as alternative nomenclature
Parathyroid adenoma Most are extrathyroidal in location; evaluate for capsule separating
lesion from thyroid; correlate with parathyroid hormone level
Malignant
PTC
Follicular thyroid carcinoma
Medullary thyroid carcinoma
Anaplastic thyroid carcinoma
Lymphoma Treat with systemic therapy rather than thyroidectomy
Metastatic disease
Note that benign and malignant nodules may have overlapping appearances and can only be differentiated by FNAB.
Different pathology laboratories may use slightly different cytologic descriptions.
Fig. 9. Parathyroid adenoma. (A) The inferior parathyroid gland is typically located posterior and inferior to the
thyroid. The echogenic thyroid capsule (arrow) separates the parathyroid adenoma (P) from the thyroid. (B) The
parathyroid adenoma is quite vascular and receives its blood supply from the thyroid gland. Unlike the central
hilar flow of a lymph node, the flow within a parathyroid adenoma is peripheral/polar in distribution.

8. Thyroid Nodule Fine-Needle Aspiration Biopsy
Biopsy and cytologic evaluation
Thyroid nodules can be sampled via US guidance
or by palpation; however, in this day and age,
they should be sampled with US guidance. After
sterilization of the skin at the needle entrance site
and administration of local anesthesia, FNA
samples are obtained with small-gauge needles
with a bevel tip, typically 25 or 26 gauge. Pathologic
evaluation can be performed on site or the samples
can be transported to a laboratory for off-site
testing. The presence of at least 6 groups of benign
follicular cells, with each group containing at least
10 cells, is required for a specimen to be consid-ered
adequate and benign, per the Bethesda
System criteria.14 Other alternative criteria for ade-quacy
include the presence of abundant colloid
(suggesting a benign macrofollicular nodule) or
enough cells to suggest an alternative diagnosis,
such as lymphocytic (or Hashimoto) thyroiditis or
atypia. Aspirated thyroid nodules are classified as
benign, atypia of undetermined significance/follic-ular
lesion of undetermined significance (AUS/
FLUS), follicular neoplasm, suspicious for malig-nancy,
or malignant, per the Bethesda System
classification.14 Approximately 10% of thyroid
FNAs from most laboratories are read, however,
as nondiagnostic or inadequate.14
Management
Benign nodules are managed conservatively with
clinical and imaging follow-up whereas nodules
classified as follicular neoplasm, suspicious for
malignancy, or malignant go on to surgical man-agement.
Nodules classified as AUS/FLUS fall
into an indeterminate category, comprising be-tween
3% and 6% of total diagnoses.14 In these
cases, repeat FNA is recommended. However,
20% of these nodules remain AUS after repeat
biopsy. The risk of malignancy in these nodules is
between 5% and 15%.14
To avoid diagnostic surgery for what may ulti-mately
be a benign nodule, FNA samples can be
sent for genomic testing. The Afirma Gene Expres-sion
Classifier (AGEC) from Veracyte (South San
Francisco, California) classifies these cytologically
indeterminate nodules as either benign or malig-nant,
with a 95% negative predictive value.15
To minimize the need for a third FNA specifically
just to perform this test, additional FNA passes
are obtained at the time of the second FNA for
AGEC testing. This material is then reserved and
analyzed in the event that the repeat (or second)
FNA is also called indeterminate. A nodule classi-fied
as benign on AGEC is managed just as a
nodule classified as benign on cytology, with
imaging and clinical follow-up.15 A benign AGEC
result, therefore, negates the necessity of per-forming
surgery for diagnosis of cytologically inde-terminate
nodules. At one center, the number of
diagnostic surgeries performed for these nodules
dropped 10-fold after the implementation of
AGEC testing, and 1 surgery was avoided for
every 2 AGEC tests performed.15 A suspicious
for malignancy AGEC result correlates to a greater
than 50% risk of malignancy for the nodule, and
surgery should be performed for pathologic
diagnosis.
Preoperative Evaluation for Cervical Nodal
Metastases
Current best surgical practice in the United States
recommends central lymph node dissection at the
time of thyroidectomy as well as lateral neck
dissection if there are confirmed metastatic cervi-cal
lymph nodes. Therefore, prior to thyroidectomy,
the cervical lymph nodes should be evaluated for
lymph node metastases both with palpation and
US; if abnormal lymph nodes are suspected, FNA
should be performed. Stulak and colleagues16 in
2006 reported a sensitivity and specificity of
83.5% and 97.7% of preoperative US in the detec-tion
of lateral nodal metastasis in newly diagnosed
thyroid cancer patients, respectively. Hence, a
systematic sonographic evaluation of the neck
nodes is performed bilaterally to identify suspicious
nodes.
US features of suspicious nodes
Benign sonographic morphologic features of
lymph nodes include the presence of an echo-genic
fatty hilum, central regular hilar vascular
flow, and elongated shape. Deviations from this
appearance should be considered abnormal.
A node demonstrating cystic change or the
presence of calcification (mimicking the appear-ance
of the primary tumor) has been shown to be
100% specific for metastatic disease.17 Increased
or eccentric irregular vascularity, round shape
and/or loss of the normal elongated shape, hyper-echogenicity
of the node relative to the adjacent
strap muscles, and loss of a fatty hilum are all
features of abnormal lymph nodes. A summary of
suspicious features is in Box 1, and examples of
suspicious nodes are given in Figs. 10–12.
Metastatic disease from other primaries, how-ever,
such as squamous cell carcinoma, can pro-duce
cystic degeneration of a lymph node.
Management of suspicious nodes
Unlike the guidelines for thyroid nodule biopsy, no
specific size criteria are commonly used in regard
to lymph node biopsy. Some institutions may have
8 Coquia et al

9. their own size cutoff (ie, biopsy lymph nodes
8 mm or larger), formed by consensus between
their surgeons, endocrinologists, and radiolo-gists.
For example, at the authors’ institution,
because of the high specificity of lymph nodes
containing calcification or cystic areas in predict-ing
metastatic disease, these are biopsied
regardless of size. Those that are abnormal but
do not contain these features are usually biopsied
when 8 mm in size.
Lymph nodes that are homogeneously hypoe-choic
without an echogenic fatty hilum present
and do not demonstrate any other suspicious
features may be followed, with biopsy for those
that demonstrate interval growth or interval
The Role of Sonography in Thyroid Cancer 9
development of additional suspicious features.
Again, this particular management step may be
based on the consensus between the referring
physicians and the radiologists.
Suspicious lymph nodes can be biopsied preop-eratively
to confirm the necessity for lateral neck
dissection at the time of thyroidectomy. Because
these nodes are usually not palpable, they are
sampled under US guidance, using the same tech-nique
as described for FNA of thyroid nodules. If
the lymph node is cystic, such that it yields insuffi-cient
cells for diagnosis, the fluid can be aspirated
and sent for thyroglobulin.
Alternatively a surgeon may choose to proceed
to surgery and remove the suspicious lymph no-des
at the time of thyroidectomy. To help the sur-geon
find the nodes intraoperatively, preoperative
Fig. 10. Cystic replacement of a cervical lymph node.
The lymph node is enlarged and has a large anechoic
component, causing increased through transmission,
compatible with cystic change (C). A small area of re-sidual
soft tissue is seen within the node (arrow). A
punctate echogenic focus is seen within the soft tis-sue,
compatible with calcification.
Fig. 11. Calcifications within a lymph node. Multiple
echogenic foci (arrow) are seen within a lymph node
(arrowheads), compatible with calcification. The lymph
node is also round, another suspicious feature. The
node was biopsied, with pathology of metastatic PTC.
Box 1
Sonographic features suspicious for lymph
node metastasis
Cystic change
Calcification
Peripheral, increased, irregular, or eccentric
vascularity
Loss of the normal elongated shape (less than
2:1 ratio between long axis and short axis) or
round shape
Hyperechogenicity of the lymph node relative
to adjacent strap muscle
Loss of fatty hilum
Irregular, asymmetrically thickened cortex
Fig. 12. Abnormal lymph node vascularity. Instead of
central hilar flow, there is peripheral vascularity,
which is increased. A fatty hilum is also not seen.
This was biopsied with pathology of metastatic PTC.

10. US can be used to mark the suspicious nodes on
the skin. In more complex cases, intraoperative
US guidance can be provided.
Postoperative Surveillance
After thyroidectomy, in conjunction with laboratory
follow-up and nuclear medicine radioiodine imag-ing,
the neck is evaluated routinely with US for the
development of nodal metastases. The initial US
examination should be performed in the first 6 to
12 months and then periodically depending on
a patient’s risk for recurrence and thyroglobulin
level.12 The frequency and length of surveillance
may also be dependent on the institution, endocri-nologist,
or surgeon. The risk of recurrence either
within the thyroid bed or within the cervical lymph
nodes in PTC has been reported to between 15%
and 25%.18
The postoperative neck can be divided into
lateral and central compartments (right lateral
neck, right central neck, left lateral neck, and left
central neck), discussed previously. Disease found
in each separate compartment leads to its own
separate neck dissection. Therefore, if multiple
abnormal nodes are present in multiple compart-ments,
a suspicious node from each compartment
should be sampled to accurately plan surgical
management and decrease the extent of the
neck dissection.
Identification of thyroid cells within the lymph
node is confirmatory for lymph node metastasis.
In the event the lymph node sampling is nondiag-nostic
or indeterminate for metastatic disease,
the lymph node can be aspirated and the sample
sent for thyroglobulin assay. It is particularly help-ful
to aspirate and analyze the fluid within small
cystic areas. A thyroglobulin level in a lymph
node greater than the serum thyroglobulin level is
diagnostic for metastatic disease.
Pitfalls in the postoperative surveillance period
In one study, approximately 34% of postoperative
patients were found to have small thyroid bed nod-ules.
18 Of these nodules, only a small percentage
(9%) increased in size during the median 3-year
follow-up period, growing at a rate of 1.3 mm/y.
Furthermore, only one-third of those proved malig-nant
demonstrated interval growth. This behavior
demonstrates the slow indolent nature of papillary
thyroid cancer. Therefore, many small nodules in
the thyroid bed without suspicious features can
be observed over time.
In addition to recurrence, other masses can be
seen in the surgical bed on postoperative exami-nations,
such as residual thyroid tissue, scarring/
fibrosis, and suture granulomas. Residual thyroid
tissue may be focal and can be vascular, features
that make it difficult to differentiate from recur-rence
by imaging. FNA can be performed to differ-entiate
the mass as either malignant (compatible
with recurrence) or benign (normal residual thyroid
tissue). Scarring in the postsurgical bed can be
nonspecific in appearance but typically is nonvas-cular
and elongated, blending into the adjacent fat
and muscle. These areas can also be observed
over time for interval increase in size or develop-ment
of suspicious features that prompt biopsy.
Suture granulomas can present as focal masses
within the thyroid bed. The sonographic appear-ance
of suture granulomas has been described
as a hypoechoic lesion with central echogenic
lines or foci.19 Although echogenic foci within a
lesion may suggest microcalcification and, there-fore,
imply recurrence, features that support su-ture
granuloma include centrality of the foci,
paired foci, and foci larger than 1 mm.19 Suture
granulomas also tend to regress or resolve over
time.19
Suture granulomas also may present within the
neck, buried within the sternocleidomastoid mus-cle
or subcutaneous tissue. Neuromas may also
be seen within the neck, typically presenting as hy-poechoic
masses in close relation to the carotid
artery. Traumatic neuromas may develop after
neck dissection.20
Because many of these masses in the thyroid
bed and neck can demonstrate either no growth
or minimal growth over time, it is important to
correlate with a patient’s thyroglobulin level over
time because this may indicate residual or pro-gressive
disease.
Alcohol ablation of lymph node metastases
As an alternative to surgical management, alcohol
(ethanol) ablation can be performed in the treat-ment
of cervical lymph node metastases, espe-cially
in patients who are either poor surgical
candidates or those who wish to avoid surgery.
The ethanol is administered through percutaneous
injection under US guidance.21
SUMMARY
US plays a crucial role in the diagnosis and
management of patients with thyroid cancer. Not
only is it the best imaging modality for the detec-tion
of suspicious thyroid nodules and cervical
nodal metastases but also the imaging modality
of choice to provide guidance during the perfor-mance
of thyroid and nodal biopsies. Knowledge
of the sonographic anatomy of the thyroid gland
and nodal stations as well as features commonly
seen in malignant thyroid nodules and nodal
metastases and experience with the use of the
10 Coquia et al

11. latest state-of the art high-resolution US equip-ment
is imperative to its effective use in the
evaluation of thyroid cancer patients. A summary
of the pearls, pitfalls, and variants and what radiol-ogists
need to know is found in Boxes 2 and 3.
Many groups of physicians (radiologists, sur-geons,
and endocrinologists) are involved in the
care of patients with thyroid cancer and the rec-ommendations
and management steps discussed
in this article may vary by institution. Therefore,
multidepartmental collaboration and meetings
are essential to keeping a practice up to date to
ensure satisfaction of the referring physicians
and providing optimal patient care.
The Role of Sonography in Thyroid Cancer 11
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Box 2
Pearls, pitfalls, and variants
Hashimoto thyroiditis can present with
diffuse small nodules (6 mm) or diffuse het-erogeneity
that can appear like nodules.
Parathyroid adenomas may be confused with
thyroid nodules or lymph nodes due to their
location:
Evaluate for an echogenic line denoting
the thyroid capsule to place the lesion as
extrathyroidal in location.
Parathyroid adenomas are usually located
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Parathyroid adenomas demonstrate polar/
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Microcalcifications within thyroid nodules
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Colloid can be confused with microcalcifica-tion:
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The differential diagnosis of thyroid bed and
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Box 3
What the radiologist needs to know
In the adult population, 50% have thyroid
nodules, but only 7% are malignant.
Microcalcification has the highest specificity
for thyroid carcinoma.
Most malignant nodules are hypoechoic.
A thyroid nodule biopsy returning a diagnosis
of AUS/FLUS should be repeated with addi-tional
samples reserved for AGEC gene
testing.
Preoperative US of the neck is performed to
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The location and number of lymph node
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especially with cystic areas, should be tested
for thyroglobulin.
Thryoid bed masses may be stable in size or
show minimal growth over time; correlation
with thyroglobulin levels is imperative to
assessing the risk of recurrence when the
sonographic appearance is indeterminate.

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12 Coquia et al