Scanning the Post Thyroidectomy Neck

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Scanning the Post Thyroidectomy Neck

• Teresa M Bieker, MBA, RDMS, RDCS, RVT
• Lead Sonographer
• University of Colorado Hospital

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Objectives

• Appearance of Normal Cervical Lymph Nodes
• Appearance of Abnormal Cervical Lymph Nodes
• Identifying Zones/Levels of the Neck
• Scanning Technique and Protocol

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Background

• Thyroid cancer is the most common endocrine
  cancer
• In 2011, there where 48,020 new cases (26,550
  women, 11,470 men) and 1,740 deaths
• For 2013, American Cancer Society estimates
  60,220 new cases (46,970 women, 13,250 men) and
  1,850 deaths
• Two thirds of patients are between 20-55 with a
  mean age of 45
• Causes include
• occupational risks
• diet
• lifestyle
• parity
• family history

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Types of Thyroid Cancer

• Well Differentiated Thyroid Cancer
• Papillary
• Follicular
• Arise from thyroid follicular cells
• Account for 80-90 of all thyroid cancers
• Poorly Differentiated Thyroid Cancer
• Medullary (5-10)
• Anaplastic (1-2)

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Outcomes

• Thyroid cancer is treatable however, outcome is
  dependent on stage (I-IV)
• Five year survival rates
• Papillary 51 to gt99
• Follicular 50 to gt99
• Medullary 28 to near 100
• Anaplastic 7

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Factors Affecting Treatment/Outcomes

• Age
• Distant metastasis
• Local invasiveness
• Cervical lymph node metastasis
• Tumor size
• Multifocality
• Tumor subtype

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TNM Classification

• T Tumor
• N Node
• M Distal Metastasis

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TNM Classification
TX Primary tumor cannot be assessed T0 No
evidence of primary tumor. T1 Tumor 2 cm in
greatest dimension limited to the thyroid. T1a
Tumor 1 cm, limited to the thyroid. T1b Tumor
gt1 cm but 2 cm in greatest dimension, limited to
the thyroid. T2 Tumor gt2 cm but 4 cm in
greatest dimension, limited to the thyroid. T3
Tumor gt4 cm in greatest dimension limited to the
thyroid or any tumor with minimal extrathyroid
extension (e.g., extension to sternothyroid
muscle or perithyroid soft tissues). T4a
Moderately advanced disease. Tumor of any size
extending beyond the thyroid capsule to invade
subcutaneous soft tissues, larynx, trachea,
esophagus, or recurrent laryngeal nerve. T4b
Very advanced disease. Tumor invades prevertebral
fascia or encases carotid artery or mediastinal
vessels
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TNM Classification

• NX Regional lymph nodes cannot be assessed.
• N0 No regional lymph node metastasis.
• N1 Regional lymph node metastasis.
• N1a Metastases to Level VI (pretracheal,
  paratracheal, and prelaryngeal/Delphian lymph
  nodes).
• N1b Metastases to unilateral, bilateral, or
  contralateral cervical (Levels I, II, III, IV, or
  V) or retropharyngeal or superior mediastinal
  lymph nodes (Level VII)

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TNM Classification

• M0 No Distant metastasis
• M1 Distant metastasis

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TNM Staging
Stage T N M
Younger then 45 years Younger then 45 years Younger then 45 years
I any T any N MO
II any T any N M1
45 years and older 45 years and older 45 years and older
I T1 N0 M0
II T2 N0 M0
III T3 N0 M0
T1 N1a M0
T2 N1a M0
T3 N1a M0
IVA T4A N0 M0
T4A N1a M0
T1 N1b M0
T2 N1b M0
T3 N1a M0

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Recurrence Rates

• For well differentiated thyroid cancer, there is
  a 9-30 recurrence rate within the first decade
  after diagnosis
• Most recurrences occur within the thyroid bed or
  cervical lymph nodes
• 60-75 occur in Z3 or Z4
• 20 occur in Z6
• Tend to affect the ipsilateral neck

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Surgery

• Total or near total thyroidectomy is the standard
  treatment for thyroid cancer. Z6 lymph nodes can
  also be removed at this time
• If the lateral/cervical lymph nodes are involved,
  a neck dissection is also performed
• Ultrasound and FNA are essential for surgical
  management

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Post Operative Evaluation

• Physical palpation exam by endocrinologist/surgeon
  
• Depending on extent of disease
• Iodine 131 whole body scan
• Radioactive iodine ablation therapy
• Chest x-ray
• CT/MRI/PET
• Neck ultrasound/Labwork (6-12 months)

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Labwork

• Typically drawn every 6-12 months
• Thyroglobulin (Tg)
• Specific protein secreted from thyroid tissue
• Tg levels should be undetectable in disease free
  patients
• If Tg increases, it is likely caused by recurrent
  tumor
• Tg Antibodies
• Present in 20-25 of thyroid cancer patients
• If antibodies are positive, Tg levels are falsely
  decreased
• Tg antibodies typically decrease over several
  years
• When disease in present, antibodies can increase
• Thyroid Stimulating Hormone (TSH) - suppressed by
  medication

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Lymph Nodes

• There are approximately 300 lymph nodes in the
  neck
• Normal nodes have a cortex and medulla covered by
  a fibrous capsule
• Cortex contains lymphocytes packed together
  forming spherical lymphoid follicles
• Medulla contains trabeculae and medullary cords
  and sinuses. Multiple medullary sinuses form the
  echogenic hilum
• A main artery and vein enter/exit the node at the
  hilum

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Cervical Lymph Nodes

• jnccn.org

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Lymph Node Anatomy
training.seer.cancer.gov
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Lymph Nodes

• Common Locations
• Normal Appearance
• Abnormal Appearance

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Common Lymph Node Locations

• Arranged in chains
• Commonly visualized along
• Jugular chain
• Submandibular gland
• Supraclavicular region
• Thyroid bed

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Why Ultrasound?

• ATA recommends U/S pre and post thyroidectomy
• More sensitive in detecting lymph nodes and
  determining benign vs malignant
• More cost effective
• Quicker, non-invasive
• No radiation
• Can detect disease as small as 2-3mm (often
  before palpated or detected by Tg)
• FNA
• Very operator dependent

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Post Thyroidectomy Scanning

• 12-15 MHz, 8MHz curved
• Patient Position
• Supine with neck extended
• Elevating the head 20o in obese patients may help
• Neck rotation
• Image optimization

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Image Optimization
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Post Thyroidectomy Scanning

• Indications
• Routine screening
• Elevated TG
• Follow-up
• Correlation with NM, CT, PET
• Zones 1-7 are evaluated and imaged
• Residual thyroid tissue
• Recurrent thyroid tumor
• Abnormal lymph nodes

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Zone Landmarks
ZONES LANDMARKS NODAL GROUP
IA Midline. Anterior to the digastric muscle and superior to the hyoid bone Submental
IB Lateral to zone IA, but medial or anterior to the submandibular gland Submandibular nodes
IIA Anterior or medial to the interior jugular vein but Lateral/posterior to the submandibular gland. Superior to the hyoid bone Upper internal jugular chain. More superiorly, the parotid nodes.
IIB Posterior to the interior jugular vein Upper internal jugular chain. More superiorly, the parotid nodes.
III From the level of the hyoid bone inferiorly to the cricoid arch. Lateral to the common carotid artery. Middle internal jugular chain
IV From the level of the cricoid arch inferiorly to the level of the clavicle. Lateral to the common carotid artery. Lower internal jugular chain
VA Posterior to the sternocleidomastoid muscle, from the base of the skull to the cricoid arch Supraclavicular fossa/posterior triangle (spinal accessory chain and transverse cervical chain
VB Posterior to the sternocleidomastoid muscle from the croicoid arch to the level of the clavicle Supraclavicular fossa/posterior triangle (spinal accessory chain and transverse cervical chain
VI Anterior/medial to the common carotid arteries from the level of the hyoid to the manubrium Anterior cervical nodes, pre and paratracheal
VII Anterior/medial to the common carotid arteries, inferior to the sternal notch Anterior, upper mediastinal nodes
Sup Clav Lateral to the common carotid artery. At or inferior to the clavicle Supraclavicular nodes

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Cervical Lymph Nodes

• It is not unusual to see multiple normal nodes in
  the neck
• The number of normal nodes visualized increases
  with age
• Characterized by
• Location
• Shape
• Size
• Echogenicity
• Vascular pattern
• Presence of echogenic hilum

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Normal Lymph Nodes

• Hypoechoic cortex
• Echogenic hilum
• Strong predictor of a normal node
• Maybe difficult to visualize in small nodes
• One feeder vessel (hilar flow)
• Cylindrical or cigar shape

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Abnormal Lymph Nodes

• Lose elliptical shape and become more rounded
• Malignant cells invade the node, disrupting the
  hilum
• 96 of malignant nodes lack a fatty hilum
• Become hyperechoic with papillary invasion but
  hypoechoic with medullary and lymphoma.
• Increase in echogenicity due to the presence of
  Tg within the lymph node
• Microcalcifications
• Mixed or peripherial flow
• Cystic in advanced disease

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Lymph Node Doppler

• Hilar flow branches radially from the hilum
• Peripheral flow is present along the periphery
  of the node but does not arise from the hilar
  vessels
• Mixed hilar and peripheral flow
• Absence of flow despite optimal Doppler settings
• Literature is inconsistent on benefit of color
  and pulsed Doppler

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Zone 6 Abnormalities

• Following thyroidectomy, the paratracheal region
  should be homogeneous
• Z6 masses can include
• Postoperative scarring
• Muscle
• Necrosing fat
• Suture granulomas
• Parathyroid gland
• Lymph node
• Remnant tissue
• Metastasis

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Zone 1

• Medial or anterior to the SMG
• Midline/superior to hyoid bone
• Nodal group submental/submandibular
• Unusual to have papillary involvement in Zone 1
• Often see reactive nodes

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Zone 6

• Anterior/medial to the CCA
• From the hyoid inferiorly to the manubrium
• Nodal group anterior cervical nodes, pre and
  para tracheal
• 20 of recurrences are in Zone 6

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Zone 2

• Lateral/posterior to the SMG
• Superior to the hyoid bone (CCA bifurcation)
• Nodal group upper IJ chain, parotid nodes
• Reactive nodes can be seen in Zone 2
• Uncommon for PTC, but can occur

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Zone 3

• From the level of the hyoid (CCA bifurcation) to
  the cricoid cartilage (level of expected thyroid
  bed)
• Lateral to CCA
• Nodal group middle IJ chain
• 60-75 of recurrences are in Zone 3 or 4

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Zone 4

• From the cricoid arch to the level of the
  clavicle (thyroid bed level)
• Lateral to the CCA
• Nodal group lower IJ chain
• 60-75 of recurrences are in Zone 3 or 4

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Zone 7/Notch

• Anterior/ medial to CCA
• At or inferior to the sternal notch
• Nodal group anterior, upper mediastinal nodes
• Zone 7 vs Notch
• Zone 7 is inferior to the subclavian
• This changes surgical management. Notch nodes
  can be removed during standard thyroidectomy.
  Zone 7 nodes requires a more extensive surgery

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Supraclavicular

• Lateral to the CCA
• At or inferior to the clavicle
• Nodal group supraclavicular nodes

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Zone 5

• Posterior to sternocleidomastoid, superior to
  clavicle
• Nodal group supraclavicular fossa, posterior
  triangle
• Uncommon location for PTC recurrence

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University of Colorado Hospital Protocol

• We do not label A or B for Zones 1, 2, 5
• Evaluate Zone 5 only if palpable
• Arrow normal nodes
• If no nodes are seen, take image labeled lateral
  neck
• Zone 2 is lateral to SMG only. It does not
  extend midline.
• Measure largest or most worrisome node in each
  zone, can number others
• Measure largest or most worrisome thyroid nodule
• Take cine if unsure

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Common Pitfalls

• If less then 5mm, nodes are difficult to track
• Is the abnormality in Zone 6 reproduceable in all
  3 planes? If not, dont measure
• Can this be biopsied?
• To determine Zone 3/4 vs Zone 6, put the patient
  in a neutral position
• Thyroid bed vs Zone 6 labeling Use Z6 after
  thyroidectomy or to measure abnormality superior
  or inferior to the thyroid

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Lymph Node Summary
Normal Malignant
Echogenic fatty hilum No echogenic hilum
Cylindrical in shape Round
Hilar flow Mixed or peripheral flow
Echogenic (PTC)
Microcalcifications
Cystic in advanced disease
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Additional Reference Bieker T. Scanning the
Post-Thyroidectomy Neck Appearance and
Technique. Journal of Diagnostic Medical
Sonography. 2010. 26(5) 215-223.