Overview
Thyroid Nodule
1. Clinical Overview
Summary
A Thyroid Nodule is a Discrete Lesion Within the Thyroid Gland that is radiologically distinct from the surrounding thyroid parenchyma. Thyroid nodules are Extremely Common, Detected clinically in 4-8% of Adults by palpation and in 20-70% by high-resolution ultrasound. The overwhelming majority are Benign (>90%), including Colloid Nodules, Follicular Adenomas, and Thyroiditis. However, approximately 5-10% of nodules are Malignant (Thyroid Cancer), making accurate evaluation essential. Risk factors for malignancy include History of Head/Neck Radiation, Family History of Thyroid Cancer, Age Extremes, Male Sex, Rapid Growth, and Suspicious Ultrasound Features (U3-U5). The key investigations are Thyroid Function Tests (TFTs), Thyroid Ultrasound (With risk stratification – TI-RADS or BTA-U Classification), and Fine-Needle Aspiration Cytology (FNAC) for nodules with suspicious features or size criteria. Management depends on cytology (Thy/Bethesda classification) and clinical features: Observation for benign nodules, Diagnostic Hemithyroidectomy or Total Thyroidectomy for suspicious or malignant lesions. [1,2,3]
Clinical Pearls
"Most Thyroid Nodules are Benign": >90%. But always evaluate carefully.
"Ultrasound Appearance Determines Need for Biopsy": Not just size. Use TI-RADS/BTA-U scoring.
"Hot Nodule on Scintigraphy = Almost Always Benign": Usually toxic adenoma. Rarely malignant.
"Cold Nodule Needs Further Evaluation": May be benign or malignant.
2. Epidemiology
Demographics
| Factor | Notes |
|---|---|
| Palpable Nodules | ~4-8% of adults. |
| Incidental Nodules (Ultrasound) | ~20-70%. |
| Age | Increase with age. |
| Sex | Female >> Male (4-5:1 for nodules, But higher cancer risk in males). |
| Risk of Malignancy | ~5-10% of all nodules. Higher in certain populations. |
Risk Factors for Malignancy
| Risk Factor | Notes |
|---|---|
| History of Childhood Head/Neck Radiation | Strong risk factor. |
| Family History of Thyroid Cancer | MTC, MEN2, PTC. |
| Age Extremes | less than 20 or >60 years. |
| Male Sex | Higher proportion of malignancy per nodule. |
| Rapid Growth | |
| Fixed, Hard, Nodule | |
| Hoarseness / Vocal Cord Paralysis | Recurrent laryngeal nerve involvement. |
| Cervical Lymphadenopathy | |
| Known MEN2 / RET Mutation | Medullary thyroid cancer. |
3. Aetiology
Benign Causes (~90%)
| Cause | Notes |
|---|---|
| Colloid Nodule | Most common. Part of multinodular goitre. |
| Follicular Adenoma | Benign neoplasm. |
| Thyroiditis | Hashimoto's (Lymphocytic), Subacute, Post-partum. May appear nodular. |
| Thyroid Cyst | Simple or complex. |
| Toxic Adenoma | Functioning nodule. Hyperthyroidism. |
Malignant Causes (~5-10%)
| Cause | Notes |
|---|---|
| Papillary Thyroid Carcinoma (PTC) | ~80% of thyroid cancers. Good prognosis. |
| Follicular Thyroid Carcinoma (FTC) | ~10-15%. |
| Medullary Thyroid Carcinoma (MTC) | ~5%. From C-cells (Parafollicular). Calcitonin marker. Can be sporadic or familial (MEN2). |
| Anaplastic Thyroid Carcinoma | less than 2%. Aggressive. Poor prognosis. Elderly. |
| Lymphoma | Rare. Usually on background of Hashimoto's. |
| Metastases | Rare. Kidney, Lung, Melanoma. |
4. Clinical Presentation
Symptoms
| Symptom | Notes |
|---|---|
| Asymptomatic | Most common. Incidental finding or self-detected. |
| Neck Swelling / Lump | Palpable mass. |
| Local Compressive Symptoms | Dysphagia (Oesophageal compression). Dyspnoea (Tracheal compression). Rare unless very large or substernal. |
| Symptoms of Thyroid Dysfunction | Hyperthyroidism (Toxic adenoma): Palpitations, Weight loss, Tremor. Hypothyroidism (Hashimoto's): Fatigue, Weight gain. |
| Hoarseness | Suggests vocal cord paralysis. Concerning for malignancy. |
| Rapid Increase in Size | Concerning for malignancy or haemorrhage into cyst. |
| Pain | Rare. May indicate haemorrhage, Thyroiditis, Or rarely, Aggressive malignancy. |
Examination Findings
| Finding | Notes |
|---|---|
| Palpable Nodule | Size, Consistency (Soft, Firm, Hard), Mobility, Tenderness. |
| Moves with Swallowing | Confirms thyroid origin. |
| Cervical Lymphadenopathy | Suspicious for metastatic disease. |
| Signs of Thyroid Dysfunction | Goitre, Tremor, Tachycardia, Eye signs (Graves'). |
| Tracheal Deviation | Large goitre. |
Red Flags for Malignancy
| Feature |
|---|
| Rapid growth. |
| Fixed, Hard nodule. |
| Hoarseness / Vocal cord paralysis. |
| Cervical lymphadenopathy. |
| History of head/Neck radiation. |
| Family history of thyroid cancer or MEN2. |
| Male sex. |
| Age extremes (less than 20 or >60). |
5. Investigations
Step 1: Thyroid Function Tests (TFTs)
| Result | Interpretation |
|---|---|
| Normal (Euthyroid) | Proceed to Ultrasound. Most common. |
| Suppressed TSH (Hyperthyroid) | Suggests Toxic (Autonomous) Nodule. Proceed to Thyroid Scintigraphy. |
| Elevated TSH (Hypothyroid) | Consider Hashimoto's thyroiditis. Check TPO antibodies. |
Step 2: Thyroid Ultrasound (US)
| Purpose | Notes |
|---|---|
| Characterise Nodule | Size, Composition (Solid/Cystic/Mixed), Echogenicity, Margins, Calcifications, Shape. |
| Risk Stratification | BTA-U Score (U1-U5) or TI-RADS. |
| Assess Lymph Nodes | |
| Guide FNAC |
BTA-U Classification (UK)
| U Score | Description | Risk of Malignancy | Action |
|---|---|---|---|
| U1 | Normal. | 0% | No action. |
| U2 | Benign (Simple cyst, Isoechoic spongiform, Colloid). | less than 3% | Observe if >1cm. No biopsy usually. |
| U3 | Indeterminate (Solid, Hypoechoic, Heterogeneous, No definite suspicious features). | ~5-15% | FNAC if ≥1cm. |
| U4 | Suspicious (Solid hypoechoic with 1-2 suspicious features). | ~15-30% | FNAC if ≥1cm (Some ≥0.5cm). |
| U5 | Malignant (Classic features: Solid hypoechoic, Microcalcifications, Irregular margins, Taller than wide, Abnormal lymph nodes). | >50% | FNAC. |
Step 3: Fine-Needle Aspiration Cytology (FNAC)
| Purpose | Notes |
|---|---|
| Cytological Diagnosis | Categorise Thy1-5 (RCPath) or Bethesda I-VI. |
| Guide Management |
Thy/Bethesda Classification
| Thy (RCPath) | Bethesda | Interpretation | Malignancy Risk | Management |
|---|---|---|---|---|
| Thy1 | I | Non-Diagnostic (Inadequate). | ~5-10% | Repeat FNAC. |
| Thy2 | II | Benign. | ~0-3% | Observe. |
| Thy3a | III | Atypia of Undetermined Significance (AUS). | ~10-30% | Repeat FNAC or Diagnostic Hemithyroidectomy. |
| Thy3f | IV | Follicular Neoplasm. | ~25-40% | Diagnostic Hemithyroidectomy (Cannot distinguish adenoma from carcinoma on cytology). |
| Thy4 | V | Suspicious for Malignancy. | ~60-75% | Hemithyroidectomy or Total Thyroidectomy. |
| Thy5 | VI | Malignant. | ~97-99% | Total Thyroidectomy (Usually). |
Thyroid Scintigraphy (Radionuclide Scan)
| Indication | Nodule with Suppressed TSH (Hyperthyroidism). |
|---|---|
| Hot Nodule | Increased uptake. Autonomous functioning nodule. Very Low Risk of Malignancy (less than 1%). Treat hyperthyroidism. FNAC usually not needed. |
| Cold Nodule | Reduced uptake. May be benign or malignant. Needs Ultrasound +/- FNAC. |
6. Management
Management Algorithm
THYROID NODULE DETECTED
(Palpable or Incidental)
↓
STEP 1: TFTs
┌────────────────┴────────────────┐
TSH NORMAL TSH SUPPRESSED
(Euthyroid) (Hyperthyroid)
↓ ↓
STEP 2: Ultrasound THYROID SCINTIGRAPHY
↓
┌──────┴──────┐
HOT COLD
NODULE NODULE
↓ ↓
~Benign Ultrasound +
Treat FNAC as below
Hyperthyroid
↓
STEP 2: ULTRASOUND (Risk Stratification)
- BTA-U Score (U1-U5) or TI-RADS
↓
FNAC INDICATIONS (Based on US Features)
- U3 nodule ≥1 cm
- U4 nodule ≥1 cm (Some ≥0.5 cm)
- U5 nodule (All sizes)
- U2 nodule: Usually observe (FNAC if >2-3cm or symptomatic)
↓
STEP 3: FNAC CYTOLOGY (Thy Classification)
┌────────────────┬────────────────┬────────────────┐
THY1 THY2 THY3-5
(Non-Diagnostic) (Benign) (Indeterminate/
Suspicious/Malignant)
↓ ↓ ↓
Repeat FNAC OBSERVE PROCEED TO
(3-6 months) (Annual US if APPROPRIATE Mx
indicated)
↓
### Surgical Atlas: Thyroid Surgery
#### 1. Hemithyroidectomy (Lobectomy)
* **Indication**:
* Diagnostic for Thy3 (Indeterminate) nodules.
* Treatment for benign compressive nodules (one side).
* Treatment for small (<1cm) low-risk papillary cancers.
* **Technique**:
* **Incision**: Collar incision (Kocher's) in a skin crease. 2-3cm above sternal notch.
* **Flaps**: Platysma raised. Strap muscles separated in midline.
* **Vessels**: Middle thyroid vein ligated first. Superior pole vessels ligated close to gland (avoid External Laryngeal Nerve). Inferior thyroid scans clipped.
* **Nerve**: **Recurrent Laryngeal Nerve (RLN)** identified in the tracheo-oesophageal groove. **Must be visualised and preserved**.
* **Parathyroids**: Identification and preservation of Superior and Inferior Parathyroid glands.
* **Prognosis**: Patient usually euthyroid post-op (other lobe takes over). Low risk of hypocalcaemia.
#### 2. Total Thyroidectomy
* **Indication**:
* Proven Malignancy (Thy5).
* Bilateral multinodular goitre.
* Graves' disease (failed medical/RAI).
* **Technique**: Same as above, repeated on both sides.
* **Risks**:
* **Bilateral RLN Injury**: Airway obstruction (cords detached in paramedian position). Need Tracheostomy.
* **Hypoparathyroidism**: Transient (20%) or Permanent (2%). Causes Hypocalcaemia.
#### 3. Neck Dissection
* **Central (Level VI)**: Paratracheal nodes. Often done prophylactically in cancer. Increased risk to Parathyroids/RLN.
* **Lateral (Level II-IV)**: Done if clinically positive nodes (N1b).
---
### Deep Dive: Follicular Adenoma vs Carcinoma
Why can't FNA distinguish them?
* **Cytology (Needle)**: Shows follicular cells. Both Adenoma and Carcinoma look the same (sheets of follicular cells).
* **Histology (Whole Nodule)**:
* **Adenoma**: Encapsulated. No invasion.
* **Carcinoma**: **Capsular Invasion** (breaks through the capsule) or **Vascular Invasion** (cells in blood vessels).
* **Implication**: You CANNOT diagnose Follicular Cancer on FNA. You must remove the lobe (Hemithyroidectomy) to check the capsule.
* *Note*: Papillary cancer is different - it has specific nuclear features ("Orphan Annie eyes") visible on FNA.
7. Complications
7. Advanced Complications
Recurrent Laryngeal Nerve (RLN) Injury
- Anatomy: Branches from Vagus. Loops under Aortic Arch (Left) or Subclavian (Right). Ascends in TE groove.
- Unilateral Injury: Hoarse, breathy voice. Bovine cough (cannot close glottis).
- Management: Speech therapy. Injection laryngoplasty (bulking).
- Bilateral Injury: Airway Emergency. Cords paralyze in adducted (closed) position. Stridor on extubation.
- Management: Re-intubation. Tracheostomy.
Hypocalcaemia (Hypoparathyroidism)
- Cause: Removal or devascularisation of the 4 parathyroid glands. (Commonest after Total Thyroidectomy / Central Neck Dissection).
- Presentation: Perioral paraesthesia ("tingling lips"), cramping (tetany), Chvostek's sign (facial twitch), Trousseau's sign (carpopedal spasm).
- Management:
- Acute: IV Calcium Gluconate (10ml 10%).
- Chronic: Oral Calcium + Alfacalcidol (Activated Vitamin D - because kidney activation needs PTH).
Thyroid Storm (Thyrotoxic Crisis)
- Rare. Can be precipitated by surgery on a toxic gland (handling releases hormone).
- Features: Hyperpyrexia (>40°C), Tachycardia (>140), Agitation, Coma.
- Tx: Beta-blockers (Propranolol), Propylthiouracil (PTU), Steroids.
8. Technical Appendix: The Cancer Types
1. Papillary Carcinoma (PTC)
- "Popular": Most common (80%).
- "Palpable": Lymph node spread is common.
- "Positive": Excellent prognosis.
- Features: Orphan Annie Nuclei, Psammoma Bodies.
- Tx: Total Thyroidectomy + RAI. (Hemithyroidectomy for <1cm T1a).
2. Follicular Carcinoma (FTC)
- "Far Away": Haematogenous spread (Bone, Lungs). Node spread rare.
- "Female": More common in women.
- Tx: Total Thyroidectomy + RAI.
3. Medullary Carcinoma (MTC)
- "MEN2": Associated with MEN2a/2b (RET oncogene).
- "Marker": Calcitonin (from Parafollicular C-cells). Amyloid stroma.
- Tx: Surgery ONLY. (Does not take up Iodine -> RAI useless).
4. Anaplastic Carcinoma
- "Awful": Elderly. Rapidly growing neck mass. Hoarseness.
- "Aggressive": Often inoperable. Palliative RT/Chemo. Death in months.
9. Prognosis and Outcomes
Survival Rates (5-Year)
- Papillary: >98% (Stage I-II).
- Follicular: >90%.
- Medullary: ~80%.
- Anaplastic: <10%.
10. Evidence and Guidelines
Key Guidelines
- British Thyroid Association (BTA): Guidelines for the Management of Thyroid Cancer (2014).
- American Thyroid Association (ATA): Management Guidelines for Adult Patients with Thyroid Nodules (2015).
- Shift: Trend towards less aggressive surgery (Lobectomy for low-risk 1-4cm cancers) to save the nerve/parathyroids.
11. Patient and Layperson Explanation
(As per original - restored)
What is a Thyroid Nodule?
A thyroid nodule is a lump in the thyroid gland (Butterfly-shaped gland in your neck). They are very common and usually benign (Not cancer).
How is it investigated?
- Blood Tests: Check thyroid hormone levels.
- Ultrasound Scan: Looks at the nodule's characteristics.
- Fine-Needle Biopsy (FNA): A small sample is taken with a needle to check the cells.
Does everyone need a biopsy?
No. Biopsy is recommended only for nodules that have certain concerning features on ultrasound or are a certain size.
When is surgery needed?
- If the biopsy shows cancer or is suspicious.
- If the biopsy shows "follicular neoplasm" (Need surgery to confirm if benign or malignant).
- If the nodule is large and causing symptoms (Difficulty swallowing/Breathing).
12. References
(As per original)
Primary Sources
- Perros P, et al. Guidelines for the management of thyroid cancer (BTA Guidelines). 2014.
- Haugen BR, et al. 2015 ATA Guidelines. Thyroid. 2016.
13. Examination Focus
(As per original)
Common Exam Questions
- Investigation of Choice (Suppressed TSH): "What investigation is indicated for a thyroid nodule with suppressed TSH?"
- Answer: Thyroid Scintigraphy (To determine if nodule is "hot" or "cold").
- Hot vs Cold Nodule: "Significance of 'hot' nodule?"
- Answer: Hot nodule = Autonomous functioning nodule = Very low risk of malignancy (<1%).
- Thyf Classification: "What does Thy3f cytology mean?"
- Answer: Follicular Neoplasm. Cannot distinguish adenoma from carcinoma on cytology. Needs Diagnostic Hemithyroidectomy.
- Papillary Features: "Histological features of PTC?"
- Answer: Orphan Annie Nuclei, Psammoma Bodies, Nuclear grooving.
Viva Points
- Retrosternal Goitre: "Pemberton's Sign". Raising arms causes facial congestion (thoracic inlet obstruction).
- Berry's Ligament: Posterior suspensory ligament. The RLN runs close to it - danger zone in surgery.
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