Thyroid Nodules: Types, Diagnosis, and Management

1. Types of Thyroid Nodules

A. Benign Nodules (majority)

"The majority of thyroid nodules are benign neoplasms and include colloid nodules, degenerative cysts, nodular hyperplasia and follicular adenomas." - Sabiston Textbook of Surgery, p. 1503

B. Malignant Nodules (in decreasing frequency)

"The most common malignant diagnosis is PTC, and in decreasing order of frequency also includes FTC, oncocytic carcinoma (OCA), MTC, PDTC, and ATC; other rare malignancies including primary thyroid lymphoma and metastasis to the thyroid gland can occur." - Sabiston Textbook of Surgery, p. 1503

C. Functional Status (Scintigraphic Classification)

2. Diagnostic Approach

Step 1: History & Physical Examination

• Age <20 or >70 years
• Male sex
• History of neck irradiation (risk increases linearly from 6.5-2000 cGy; peaks 20-30 years post-exposure)
• Rapid growth, hoarseness, dysphagia, dyspnea (compressive/infiltrative signs)
• Firm, fixed, immobile nodule >3-4 cm
• Cervical lymphadenopathy
• Family history of thyroid cancer or MEN syndrome
• Pheochromocytoma or hyperparathyroidism (suggests MEN 2)

"Patients younger than 20 years have an approximately 20-50% incidence of malignancy when presenting with a solitary thyroid nodule." - Cummings Otolaryngology, p. 3544

Step 2: Serum TSH

Step 3: Neck Ultrasound

1. Parenchymal pattern and gland size
2. Nodule size, location, and characteristics
3. Cervical lymph node status (central and lateral compartments)

• Microcalcifications
• Hypoechoic solid nodule
• Taller-than-wide shape
• Irregular/microlobulated margins
• Extrathyroidal extension
• Increased intranodular vascularity
• Associated abnormal lymph nodes

ATA Sonographic Risk Stratification (from Current Surgical Therapy 14e):

ACR TI-RADS System

FDG-PET incidental thyroid nodules carry a higher cancer risk - FNA recommended at >1 cm threshold. - Current Surgical Therapy 14e, p. 1705

Step 4: Fine-Needle Aspiration (FNA) Biopsy

Step 5: Molecular Testing (for Bethesda III-IV)

• Afirma Gene Expression Classifier (GEC/GSC) - "rule-out" test (high NPV)
• ThyroSeq v3 - Next-generation sequencing of 112 genes; analyzes mutations, gene fusions, copy number alterations - both rule-out and rule-in
• ThyGenX/ThyraMIR and Rosetta GX Reveal - Less clinical data

Step 6: Additional Tests

• Serum calcitonin - Useful for diagnosis/surveillance of MTC; routine screening not standard in the US
• Serum thyroglobulin - Useful for post-treatment surveillance of differentiated thyroid cancer, NOT for initial diagnosis
• CT/MRI - Reserved for locally advanced disease, substernal extension, or suspected metastases
• Genetic testing (RET mutations) - Mandatory in all MTC patients; enables family screening

3. Diagnostic Algorithm

4. Management

Benign Nodules (Bethesda II)

• Observation with periodic US (typically 6-18 months, then every 2-3 years)
• No role for T4 suppression (ineffective in iodine-replete populations and carries cardiovascular/skeletal risks)
• Indications for repeat FNA: growth >20% in two dimensions, or change in ultrasound features
• Surgical indications for confirmed benign nodules: cosmetic concern, compressive symptoms (dysphagia, dyspnea), or patient preference

Hot/Toxic Nodule

• Radioiodine (I-131) or surgical resection (lobectomy)
• Antithyroid drugs as bridge to definitive treatment

Indeterminate Nodules (Bethesda III-IV)

• Molecular testing first if available - guides whether to observe or operate
• If molecular testing suggests low risk: surveillance with repeat US/FNA
• If molecular testing suggests high risk, or testing unavailable: diagnostic lobectomy
• A diagnosis of follicular neoplasm (Bethesda IV) always requires surgery (cannot distinguish adenoma from carcinoma by FNA alone)

Malignant/Suspicious Nodules (Bethesda V-VI)

• Surgical resection is the primary treatment
• Lobectomy vs. total thyroidectomy: Decision based on cancer size, risk features, patient factors; ATA guidelines support lobectomy for low-risk PTC <1 cm without extrathyroidal extension or lymph node involvement
• Preoperative US of cervical lymph nodes is mandatory before any thyroid cancer surgery
• Radioactive iodine (RAI) ablation - for differentiated thyroid cancer with high-risk features post-thyroidectomy
• TSH suppression therapy - Post-operative levothyroxine to maintain TSH below normal range in high-risk DTC
• External beam radiation - For anaplastic carcinoma, lymphoma (often highly radiosensitive), or cases with gross residual disease
• Targeted therapy - Kinase inhibitors (sorafenib, lenvatinib) for radioiodine-refractory metastatic DTC; vandetanib/cabozantinib for MTC; BRAF/MEK inhibitors for ATC with BRAF V600E mutations

Active Surveillance for Low-Risk PTC

5. Special Considerations

• Multinodular goiter: Risk of malignancy per nodule is the same as for a solitary nodule; dominant nodule or those with suspicious US features should be biopsied
• Substernal goiter: Most can be removed via cervical incision; posteriorly extending or infraaortic goiters may require sternotomy
• Pediatric nodules: 20-50% malignancy risk; treat more aggressively
• Pregnancy: US-guided FNA acceptable; surgery deferred to second trimester if possible; RAI is contraindicated

• Sabiston Textbook of Surgery, 21st ed., pp. 1502-1503
• Harrison's Principles of Internal Medicine, 22nd ed. (2025), pp. 3091-3093
• Cummings Otolaryngology Head and Neck Surgery, pp. 3535-3674
• Current Surgical Therapy, 14th ed., pp. 1713-1755
• Schwartz's Principles of Surgery, 11th ed., p. 1669
• 2023 ETA Clinical Practice Guidelines (PMID: 37358008)
• 2024 Japan Endocrine Surgery Guidelines (PMID: 40058844)