Scanning the Post Thyroidectomy Neck

Teresa M Bieker, MBA, RDMS, RDCS, RVTLead Sonographer

University of Colorado Hospital

Appearance of Normal Cervical Lymph Nodes

Appearance of Abnormal Cervical Lymph Nodes

Identifying Zones/Levels of the Neck

Scanning Technique and Protocol

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

dietlifestyleparityfamily history

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%)

Thyroid cancer is treatable; however, outcome is dependent on stage (I-IV)

Five year survival rates:

Papillary: 51% to >99%

Follicular: 50% to >99%

Medullary: 28% to near 100%

Anaplastic: 7%

Age

Distant metastasis

Local invasiveness

Cervical lymph node metastasis

Tumor size

Multifocality

Tumor subtype

T = Tumor

N = Node

M = Distal Metastasis

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 >1 cm but ≤2 cm in greatest dimension, limited to the thyroid.

T2: Tumor >2 cm but ≤4 cm in greatest dimension, limited to the thyroid.

T3: Tumor >4 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

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)

M0: No Distant metastasis

M1: Distant metastasis

Stage T N M

Younger then 45 years

I any T any N MO

II any T any N M1

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

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

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

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)

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

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

training.seer.cancer.gov

Common Locations

Normal Appearance

Abnormal Appearance

Arranged in chains

Commonly visualized along:

Jugular chain

Submandibular gland

Supraclavicular region

Thyroid bed

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

12-15 MHz, 8MHz curved

Patient Position

Supine with neck extended

Elevating the head 20o in obese patients may help

Neck rotation

Image optimization

Indications: Routine screening Elevated TG Follow-upCorrelation with NM, CT, PET

Zones 1-7 are evaluated and imaged

Residual thyroid tissueRecurrent thyroid tumorAbnormal lymph nodes

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

IIAAnterior 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 veinUpper internal jugular chain. More superiorly, the parotid nodes.

IIIFrom the level of the hyoid bone inferiorly to the cricoid arch. Lateral to the common carotid artery.

Middle internal jugular chain

IVFrom the level of the cricoid arch inferiorly to the level of the clavicle. Lateral to the common carotid artery.

Lower internal jugular chain

VAPosterior 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

VBPosterior 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

VIAnterior/medial to the common carotid arteries from the level of the hyoid to the manubrium

Anterior cervical nodes, pre and paratracheal

VIIAnterior/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

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

Hypoechoic cortex

Echogenic hilumStrong predictor of a normal nodeMaybe difficult to visualize in small nodes

One feeder vessel (hilar flow)

Cylindrical or cigar shape

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

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

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

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

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

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

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

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

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

Lateral to the CCA

At or inferior to the clavicle

Nodal group: supraclavicular nodes

Posterior to sternocleidomastoid, superior to clavicle

Nodal group: supraclavicular fossa, posterior triangle

Uncommon location for PTC recurrence

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

If less then 5mm, nodes are difficult to track

Is the abnormality in Zone 6 reproduceable in all 3 planes? If not, don’t 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

Additional Reference: Bieker T. Scanning the Post-Thyroidectomy Neck:

Appearance and Technique. Journal of Diagnostic Medical Sonography.

2010. 26(5): 215-223.