Thyroid Nodule

What is a Thyroid Nodule?

A thyroid nodule is a lump or growth within the thyroid gland in the neck. Ultrasound is the best imaging tool for detecting and characterizing thyroid nodules.

Imaging Appearance

On thyroid ultrasound, nodules are characterized by:

Composition:

• Solid - Uniform tissue texture
• Cystic - Fluid-filled
• Mixed - Both solid and cystic components

Echogenicity (Brightness):

• Hypoechoic - Darker than surrounding thyroid (higher cancer risk)
• Isoechoic - Same brightness as thyroid
• Hyperechoic - Brighter than thyroid (usually benign)

Suspicious Features:

• Microcalcifications - Tiny bright spots (concerning)
• Irregular margins - Ill-defined borders
• Taller than wide - Vertical orientation
• Increased blood flow - On Doppler imaging
• Extrathyroidal extension - Grows beyond thyroid capsule

How Common are Thyroid Nodules?

Very Common:

• Palpable nodules: 5% of women, 1% of men
• Ultrasound-detected nodules: 19-68% of adults
• Incidental findings on CT/MRI: 16%
• Prevalence increases with age

Most Are Benign:

• 90-95% are benign
• 5-10% are malignant
• Women affected 3x more than men

Risk Assessment - TI-RADS Classification

Radiologists use the Thyroid Imaging Reporting and Data System (TI-RADS) to stratify cancer risk:

TR1 (Benign): 0% malignancy risk

• Pure cyst

TR2 (Not Suspicious): ＜ 2% risk

• Spongiform appearance

TR3 (Mildly Suspicious): 2-5% risk

• Isoechoic, no suspicious features

TR4 (Moderately Suspicious): 5-20% risk

• Hypoechoic with some worrisome features

TR5 (Highly Suspicious): ＞ 20% risk

• Multiple concerning features
• Microcalcifications, irregular margins, taller than wide

Symptoms

Most Nodules Are Asymptomatic

Discovered incidentally on:

• Physical exam
• Imaging for other reasons (carotid ultrasound, CT scan)
• Patient noticing neck lump

When Large (＞ 3-4 cm)

• Visible neck lump
• Difficulty swallowing
• Sensation of pressure in neck
• Hoarseness (if pressing on recurrent laryngeal nerve)
• Shortness of breath (if compressing trachea)

Functional Nodules (Rare)

Hot Nodules (produce excess thyroid hormone):

• Hyperthyroidism symptoms
• Weight loss, rapid heartbeat, anxiety
• Always benign (＜ 1% cancer risk)

Diagnosis

1. Thyroid Ultrasound

• First-line imaging test
• Evaluates size, composition, suspicious features
• Assesses lymph nodes

2. Blood Tests

Thyroid Function:

• TSH (thyroid-stimulating hormone) - Most important
• Free T4 (thyroxine)
• Low TSH suggests hot nodule → get thyroid scan

If Medullary Cancer Suspected:

• Calcitonin level

3. Fine Needle Aspiration (FNA) Biopsy

Indications:

• TR5 nodules ≥ 1 cm
• TR4 nodules ≥ 1.5 cm
• TR3 nodules ≥ 2.5 cm
• Any size if concerning lymph nodes

Procedure:

• Thin needle guided by ultrasound
• Extracts cells for microscopic analysis
• Diagnostic accuracy: 90-95%

Results (Bethesda Classification):

• I - Non-diagnostic: Repeat biopsy
• II - Benign: Observation
• III/IV - Indeterminate: May need molecular testing or surgery
• V - Suspicious for malignancy: Surgery
• VI - Malignant: Surgery

4. Molecular Testing (For Indeterminate Nodules)

• Gene mutation analysis
• Helps determine cancer risk
• Guides decision about surgery

Treatment

Benign Nodules (90-95%)

Observation (Active Surveillance):

• Repeat ultrasound in 12-24 months
• If stable, extend intervals
• No treatment needed unless symptomatic

Surgery Considered If:

• Large size causing compressive symptoms
• Cosmetic concerns
• Patient preference

Thyroid Hormone Suppression:

• No longer recommended
• Does not shrink nodules effectively
• Risk of hyperthyroidism

Malignant Nodules (5-10%)

Surgical Treatment:

Total Thyroidectomy:

• Removal of entire thyroid gland
• Standard for most thyroid cancers
• Requires lifelong thyroid hormone replacement

Lobectomy (Hemithyroidectomy):

• Removal of one thyroid lobe
• Option for small, low-risk papillary cancers (＜ 4 cm)
• May not need hormone replacement

Additional Treatments:

• Radioactive iodine (I-131): For higher-risk cancers
• External radiation: Rarely needed
• Targeted therapy: For advanced cases

Minimally Invasive Options (Select Cases)

Radiofrequency Ablation (RFA):

• Heat probe destroys nodule
• For benign nodules causing symptoms
• Not FDA-approved in US for thyroid

Ethanol Ablation:

• For purely cystic nodules
• Collapses cyst

Types of Thyroid Cancer

Papillary Thyroid Cancer (80%):

• Most common type
• Excellent prognosis (＞ 95% cure rate)
• Slow-growing

Follicular Thyroid Cancer (10-15%):

• Generally good prognosis
• May spread through blood

Medullary Thyroid Cancer (3-5%):

• Arises from C cells
• May be hereditary (MEN2 syndrome)
• Elevated calcitonin

Anaplastic Thyroid Cancer (＜ 2%):

• Aggressive, rare
• Poor prognosis
• Rapidly growing

Prognosis

Benign Nodules:

• Excellent prognosis
• Most remain stable
• 1-3% may grow slowly over years
• Very low risk of becoming cancerous

Thyroid Cancer:

• Overall 5-year survival: 98%
• Papillary cancer: ＞ 99% for localized disease
• Most thyroid cancers are highly treatable
• Long-term monitoring required

What Should You Do?

If a thyroid nodule is found:

1. Get TSH Level:

• Determines if nodule is functional

2. Risk Stratify:

• Review ultrasound features with your doctor
• Determine if biopsy is needed

3. If Biopsy Recommended:

• FNA is quick, safe, minimal discomfort
• Diagnostic accuracy is high

4. If Benign:

• Follow-up ultrasound surveillance
• No immediate treatment needed
• Report new symptoms

5. If Malignant:

• Consult endocrine surgeon
• Discuss surgical options
• Prognosis is excellent for most types

Prevention

No proven prevention strategies, but:

• Adequate iodine intake reduces goiter risk
• Avoid unnecessary radiation exposure to neck
• Regular check-ups if family history of thyroid disease

Related Imaging Terms

• Multinodular goiter - Multiple thyroid nodules
• Thyroid cyst - Fluid-filled nodule
• Hashimoto's thyroiditis - Autoimmune thyroid inflammation

Common Questions

Should I have the nodule removed?

Not necessarily. Most benign nodules don't require surgery unless causing symptoms or cosmetic concerns.

How often do I need follow-up ultrasound?

Typically 12-24 months for benign nodules. If stable for 2 exams, intervals may be extended.

Can nodules go away?

Some cystic nodules may shrink or resolve, but solid nodules rarely disappear.

Does a thyroid nodule mean I have thyroid problems?

Not always. Most nodules don't affect thyroid function (TSH is normal).

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Medical Disclaimer: This information is educational. Consult an endocrinologist or endocrine surgeon for evaluation and management of thyroid nodules.