THYROID MALIGNANCY

Anatomy

Thyroid Malignancy

•Patients presenting with a palpable thyroid is a common clinical dilemma.•They are four times more common in women then in men.

Papillary carcinoma Follicular carcinoma Anaplastic carcinoma Medullary carcinoma Lymphoma Hurthle cell carcinoma Metastasis from other primary tumors

Types Of Thyroid Cancer

Ultrasound

Radionuclide scan

CT scan

PET scan

MRI

Imaging Modalities

Detection and characterization of thyroid cancer

Detection of cervical nodal metastases

Follow-up of patients after treatment for early detection of local or nodal tumor recurrence

Provide imaging guidance for FNAC or biopsy.

Major Role of Ultrasound In Thyroid Malignancy

Treatment with radioactive iodine for residual malignant thyroid tissue and metastatic disease in patients with well-differentiated thyroid carcinoma after total thyroidectomy.

Major Role Of Radionuclide Scan In Thyroid Malignancy.

Evaluate extrathyroid spread of tumor to adjacent structures such as the larynx, trachea and vessels within the carotid sheath and provide evidence of regional or distant metastases

Role Of CT & MRI In Thyroid Malignancy

Echogenicity The incidence of malignancy is 4% when a

solid thyroid nodule is hyperechoic.

If the lesion is hypoechoic ,the incidence of malignancy rises to 26%

Ultrasound Features Of Thyroid Nodules

Ultrasound Features Of Thyroid Nodules

Margins • malignant thyroid nodule tends to have ill-defined margins.

• A peripheral halo of decreased echogenicity is seen around hypoechoic and isoechoic nodules.

Calcification Fine punctate calcification due to calcified

psammoma bodies within the nodule is seen in papillary carcinoma in 25%–40% of cases.

Coarse, dysmorphic or curvilinear

calcifications commonly indicate benignity .

Longitudinal grey scale sonogram shows characteristic punctate calcification (arrowheads) within an ill-defined solid hypoechoic thyroid nodule (arrows) which is highly suggestive of papillary carcinoma .

Longitudinal grey scale sonogram shows coarse calcifications (arrows) with dense shadowing within a thyroid nodule suggestive of benign calcification.

This indicates presence of colloid within the nodule and thus its benign nature.

Comet tail sign

Transverse grey scale sonogram shows the presence of comet-tail artifacts (arrowheads) within a predominantly cystic thyroid nodule (arrows). Features are of a benign colloid nodule. Curved arrow identifies the internal jugular vein and asterisk marks the common carotid artery.

Presence of cystic component is a feature of benign nature of a nodule.

However some papillary carcinomas demonstrate cystic component which mimic benign nodule, but the presence of punctate calcification in solid component helps in diagnosis.

Solid/cystic

Longitudinal grey scale sonogram shows a well-defined heterogeneous thyroid nodule (arrows) with a large cystic component (arrowheads) and septation (open arrows). Features are compatible with a benign hyperplastic nodule.

Transverse grey scale sonogram shows a cystic component (open arrows) within a papillary carcinoma (arrows) of the thyroid. The presence of punctate calcification (arrowheads) identifies its malignant nature.

Multinodularity

It is a myth that multinodularity implies benignity.

Colour flow patterns

In general there are three patterns of vascular distribution within a thyroid nodule .

Type I: complete absence of flow signal within the nodule.

Type II: exclusive perinodular flow signals. Type III: intranodular flow with multiple vascular poles

chaotically arranged, with or without significant perinodular vessels.

Type III pattern is generally associated with malignancy. Types I and II are more commonly seen in benign

hyperplastic nodules

Papillary carcinoma accounts for 60%–70% of all thyroid malignancies.

peak incidence in the third and fourth decades. Females are more commonly affected than males.

The tumour commonly spreads along the rich lymphatic system within and adjacent to the thyroid gland accounting for the multifocal nature of the tumour within the thyroid gland and its spread to regional lymph nodes.

Venous invasion occurs in 7% of papillary carcinomas and distant metastases to bone and lung are seen in 5%–7%

Papillary Carcinoma

Predominantly solid (70%) and hypoechoic (77%–90%)

Presence of punctate microcalcification (25%–90%) , correspond to psammomas bodies on microscopy

ill-defined margins.

Chaotic intranodular vascularity on colour flow imaging

Adjacent characteristic lymph nodes located in the pre-/paratracheal regions and along the cervical chains.

Cystic necrosis in 25%.

Ultrasound Features Of Papillary Carcinoma

Transverse grey scale sonogram shows a solid, ill-defined, hypoechoic nodule (arrows) containing punctate calcification (arrowheads) in the right lobe of thyroid gland. Features are typical of papillary carcinoma of thyroid. Asterisk identifies the common carotid artery and curved arrow the trachea.

Transverse grey scale sonogram shows multiple round, solid, slightly hyperechoic cervical lymph nodes (arrows) with punctate calcification (arrowheads) in upper jugular chain. Features are suggestive of metastatic lymph nodes from primary papillary carcinoma of thyroid. Curved arrow identifies the internal jugular vein and asterisk marks the common carotid artery.

Transverse grey scale sonogram shows multiple enlarged hypoechoic cervical lymph nodes (arrows) with internal cystic necrosis (arrowheads) in a patient with metastatic lymphadenopathy from papillary carcinoma of thyroid.

Anaplastic Carcinoma• Anaplastic carcinoma is one of the most aggressive head and neck cancers and has a grave prognosis.

• It accounts for 15%–20% of all thyroid cancers .

• The diagnosis is suspected clinically with rapid growth in a long-standing thyroid nodule.

• Patients frequently present with signs and symptoms of airway compression.

Hypoechoic tumour diffusely involving the entire lobe or gland

ill-defined margin Areas of necrosis in 70%.

Nodal or distant metastases in 80% of patients ; the involved lymph nodes show evidence of necrosis in 50% .

Multiple small intranodular vessels on colour flow imaging

Extracapsular spread and vascular invasion in a third of patients.

Ultrasound Features Of Anaplastic Carcinoma

Transverse grey scale sonogram shows a large, solid, hypoechoic mass (arrows) occupying the right lobe of thyroid gland. Note the presence of extra-thyroid spread posteriorly (arrowheads). Histology: anaplastic carcinoma. Curved arrow identifies the internal jugular vein and asterisk marks the common carotid artery.

Medullay carcinoma is believed to arise from parafolloicular C-cells.

It represents 5% of thyroid cancer. 50% have nodal metastasis and 15-25%

have distant metastasis to lungs, liver and brain.

May be associated with pheochromocytoma and MEN syndrome.

Recurrence in the neck and mediastinum is common.

Medullary carcinoma

solid hypoechoic nodule echogenic foci in 80%–90% of tumours due to

amyloid deposition and associated calcification . similar deposits are also seen in 50%–60% of associated nodal metastases

chaotic intranodular vessels within the tumour on colour flow imaging.

Ultrasound Features Of Medullary Carcinoma

Transverse grey scale sonogram shows an ill-defined, solid, hypoechoic mass (arrows) occupying the left lobe of the thyroid gland. Multiple echogenic foci (arrowheads) casting dense posterior acoustic shadowing probably related to amyloid deposition and associated calcification. Appearance is that of a medullary carcinoma. Note how it closely resembles a papillary carcinoma. Curved arrow identifies the trachea and asterisk marks the common carotid artery.

A follicular thyroid lesion comprises follicular adenoma and follicular carcinoma which can only be distinguished on histology of the surgical specimen by the presence/absence of vascular and capsular invasion. Therefore it is often not possible to differentiate a benign from a malignant follicular lesion with FNAC or core biopsy.

A follicular carcinoma accounts for 2%–5% of all thyroid cancers.

It has propensity for haematogenous metastases to lungs, liver, bone and brain.

Nodal metastases in the neck are less commonly encountered.

Follicular Carcinoma

hyperechoic/isoechoic in echotexture.Hypoechoic lesions have a higher risk of being malignant .

Ultrasound Features of Follicular Lesions

.

• predominantly solid and homogeneous in 70% well-defined, haloed in 80% .

• benign lesions have a type II vascularity, whereas malignant lesions have a type III vascularity .

Longitudinal grey scale sonogram shows a well-defined hyperechoic nodule (arrows) in the left lobe of thyroid gland suggestive of a follicular lesion

Longitudinal grey scale sonogram shows an ill-defined heterogeneous thyroid nodule (arrows). The hypoechoic nature of the follicular lesion raises the suspicion of follicular carcinoma which was confirmed on subsequent thyroidectomy.

The only reliable signs of malignancy on ultrasound include frank vascular invasion to adjacent vessels (such as internal jugular vein and common carotid artery) and extracapsular spread.

Longitudinal grey scale sonogram shows the presence of floating hypoechoic thrombus (arrowheads) within the distended internal jugular vein (arrows). Colour/power Doppler will demonstrate vascularity in a tumour thrombus which distinguishes it from a stasis venous thrombus.

Metastases to the thyroid gland is infrequent; the incidence in patients with known primary is 2%–17% .

Metastases to the thyroid are due to haematogenous spread, most commonly from primary melanoma, breast carcinoma, renal cell carcinoma, lung carcinoma and colonic carcinoma.

Thyroid Metastasis

Homogenous; hypoechoic mass. Well-defined margins Predominantly in the lower pole. Heterogeneous echopattern when the gland

is diffusely involved . Multiple, hypoechoic solid, thyroid nodules. chaotic intranodular vascularity.

U/S Features Include

Transverse grey scale sonogram in a patient with known breast carcinoma shows a well-defined, solid, homogeneous hypoechoic mass (arrows) occupying the right lobe of thyroid. FNAC confirmed a metastatic carcinoma. The curved arrow identifies the trachea and the asterisk marks the common carotid artery.

Lymphoma accounts for 1%–3% of all thyroid malignancies.

History of Hashimoto’s thyroiditis is commonly present

Thyroid involvement is more commonly seen in non-Hodgkin’s lymphoma than in Hodgkin’s disease.

The typical clinical presentation is an elderly female with a rapidly enlarging neck mass.

Thyroid involvement may be focal or diffuse, extrathyroid spread and vascular invasion are seen in 50%–60% and 25%.

Lymphoma

Well-defined nodule with pseudocystic appearance or heterogeneous appearance

Diffuse involvement may result in heterogeneous echopattern or simple enlargement of the gland with normal echopattern –

Round, hypoechoic, reticulated lymphomatous nodes in the neck

Background of previous Hashimoto’s thyroiditis in the form of echogenic fibrous strands within the thyroid gland is often seen

Ultrasound Features of Lymphoma

Longitudinal grey scale sonogram shows an ill-defined, solid, hypoechoic nodule (arrows) in the thyroid gland. Thin echogenic lines (arrowheads) in the adjacent thyroid glandular parenchyma indicate background Hashimoto’s thyroiditis. Biopsy confirmed non-Hodgkin lymphoma of the thyroid gland.

The patient can be regularly followed up with ultrasound examination of the neck for the early detection of local and nodal tumour recurrence.

Role of ultrasound in follow-up

One has to be aware that post-operative suture granulomas may appear sonographically as hypoechoic nodules with coarse echogenic foci casting posterior acoustic shadowing in the thyroid bed.

Transverse grey scale sonogram in a patient 1 year after total thyroidectomy for papillary carcinoma shows a small hypoechoic nodule (arrows) with punctate calcification (arrowhead) in the left thyroid bed. FNAC confirmed local tumour recurrence. The curved arrow identifies the trachea, the open arrow the oesophagus and the asterisk marks the common carotid artery.

Transverse grey scale sonogram shows an ill-defined hypoechoic nodule (arrows) in the right thyroid bed containing coarse echogenic foci (arrowheads). Features are suggestive of a suture granuloma. The asterisk identifies the common carotid artery.

(a) A 70-year-old woman with follicular thyroid carcinoma. Cervical ultrasound indicated regional lymph node metastases. To confirm this finding and to determine whether there were additional lesions, FDG PET was performed which showed hot spots in the neck, upper mediastinum, the sternum and 12th thoracic vertebra (arrow). (b) Coronal slice in a 81-year-old woman showing lymph node metastases in the neck as well as mediastinum.

PET in the follow-up of differentiated thyroid cancer

The most common system used to describe the stages of thyroid cancer is the American Joint Committee on Cancer (AJCC) TNM system

STAGING

TX: Primary tumor cannot be assessed. T0: No evidence of primary tumor. T1: The tumor is 2 cm (slightly less than an inch) across or smaller and

has not grown out of the thyroid. T1a: The tumor is 1 cm (less than half an inch) across or smaller and has

not grown outside the thyroid. T1b: The tumor is larger than 1 cm but not larger than 2 cm across

and has not grown outside of the thyroid. T2: The tumor is between 2 cm and 4 cm (slightly less than 2 inches)

across and has not grown out of the thyroid. T3: The tumor is larger than 4 cm or it has begun to grow a small

amount into nearby tissues outside the thyroid. T4a: The tumor is any size and has grown extensively beyond the

thyroid gland into nearby tissues of the neck, such as the larynx (voice box), trachea (windpipe), esophagus (tube connecting the throat to the stomach), or the nerve to the larynx. This is also called moderately advanced disease.

T4b: A tumor of any size that has grown either back toward the spine or into nearby large blood vessels. This is also called very advanced disease.

T categories for thyroid cancer (other than anaplastic thyroid cancer)

All anaplastic thyroid cancers are considered T4 tumors at the time of diagnosis.

T4a: Tumor is still within the thyroid.

T4b: Tumor has grown outside of the thyroid.

T categories for anaplastic thyroid cancer

NX: Regional (nearby) lymph nodes cannot be assessed.

N0: No spread to nearby lymph nodes.

N1: The cancer has spread to nearby lymph nodes.

N1a: Spread to lymph nodes around the thyroid in the neck (called pretracheal, paratracheal, and prelaryngeal lymph nodes).

N1b: Spread to other lymph nodes in the neck (called cervical) or to lymph nodes behind the throat (retropharyngeal) or in the upper chest (superior mediastinal).

N categories for Thyroid Cancer

M0: No distant metastasis.

M1: Spread to other parts of the body, such as distant lymph nodes, internal organs, bones, etc.

M categories for Thyroid Cancer

T N MUnder 45 yearsStage 1 Any T Any N M0Stage II Any T Any N M145 years and olderStage 1 T1 N0 M0Stage II T2 N0 M0Stage III T3 N0 M0

T1 N1a M0T2 N1a M0T3 N1a M0

Stage IVA T4a N0 M0T4a N1a M0T1 N1b M0T2 N1b M0T3 N1b M0T4a N1b M0

Stage IVB T4b Any N M0Stage IVC Any T Any N M1

Sixth edition of the AJCC/UICC staging (papillary and follicular carcinoma)

Medullary I •T1, N0, M0

II •T2, N0, M0•T3, N0, M0

III •T1, N1a, M0•T2, N1a, M0•T3, N1a, M0

IVA •T4a, N0, M0•T4a, N1a, M0•T1, N1b, M0•T2, N1b, M0•T3, N1b, M0•T4a, N1b, M0

IVB •T4b, Any N, M0

IVC •Any T, Any N, M1

Sixth edition of the AJCC/UICC staging for medullary carcinoma

Anaplastic (all anaplastic cancers are considered Stage IV)

IVA •T4a, Any N, M0

IVB •T4b, Any N, M0

IVC •Any T, Any N, M1

Sixth edition of the AJCC/UICC staging for anaplastic carcinoms

Axial T1-weighted MRI post-contrast of a large anaplastic carcinoma with extensive extrathyroidal tumour extension

Axial T2-weighted MRI with fat saturation showing a papillary carcinoma (arrow heads) invading into the tracheal lumen (arrow).

Axial T1-weighted MRI post-contrast showing an anaplastic carcinoma (arrows) which is surrounding (>270°) and invading the oesophagus (arrow heads).

Axial contrast-enhanced CT scan showing metastatic nodes from a medullary carcinoma in the superior mediastinum (arrows).

computed tomography section through the thorax shows a heterogeneous mass (m) at the root of the neck, on the left, that displaces the trachea to the right. The mass appears to be growing in the caudal direction and is reaching the arch of the aorta (same patient as in the previous image).

 MRI of anaplastic carcinoma: T4b, 76-year-old woman with rapidly enlarging mass. Axial T1-WI postgadolinium image shows a large heterogeneously enhancing mass with central nonenhancing areas of necrosis. The mass arises in the left thyroid lobe but extends posteriorly to invade the prevertebral musculature (arrow) with anterior extrathyroidal extension into the strap muscles and subcutaneous soft tissue (arrowhead).

Stage T3 follicular carcinoma. Axial CECT shows a well-circumscribed solid 4.8-cm mass in the left thyroid lobe (arrow). Surgical pathology showed a follicular carcinoma.

28-year-old woman with papillary carcinoma of right lobe of thyroid. Axial CT image shows malignant mass with extrathyroidal extension (arrow) and small lymph node with contrast enhancement (arrowhead) at right level III. Ultrasound depicted no lymph node metastatic lesions in either lateral compartment. Presence of nodal metastasis was confirmed at surgery.

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