Diagnosis and Management of Thyroid Nodules

Aim: To review current medical evidence regarding the diagnosis and management of thyroid nodules.

Increased use of imaging leads to frequent discovery of incidental thyroid nodules.
- Majority are benign (over 90%).
- Importance of evaluating and monitoring concerning nodules to avoid unnecessary surgeries and complications.

Symptomatic or suspicious nodules require further evaluation using:
- Ultrasonography
- Cytopathology
Indeterminate nodules can be analyzed using:
- Molecular tests
- Liquid biopsy for further management guidance.
Active surveillance is recommended for specific malignant nodules that meet defined criteria.
Small symptomatic benign nodules may be treated with:
- Ethanol injection
- Thermal ablative techniques.
Hemithyroidectomy serves both as diagnostic for follicular neoplasm and treatment for:
- Symptomatic benign nodules
- Small solitary thyroid carcinoma.
Total thyroidectomy is indicated for:
- Symptomatic
- Hypersecreting
- Malignant multiple nodules.

Thyroid nodules are increasingly identified; only a minority require intervention.
- Importance of follow-up and accurate identification of nodules.
Ultrasonography with added features aids in risk stratification of nodules and guides cytopathology assessment.
Bethesda classification updated in 2023 helps in categorizing nodules needing further evaluation.
Advances in thermal ablative techniques present new avenues to treat certain nodules without surgery.

Prevalence of thyroid nodules varies by detection method:
- Palpation: up to 5%
- Ultrasound: 35%
- Autopsy studies: ~65%
- PET CT: up to 4% (non-thyroid reasons).
Benign nodules often are:
- Colloid-filled hyperplastic
- Inflammatory.
Malignant nodules can arise from:
- Follicular (95%)
- Parafollicular origins.
Other rare malignancies include lymphomas and sarcomas.
Male prevalence: 0.8% (higher cancer rates than females).
- Women: 5.3% prevalence of nodules. Cancer rates approximately 8% in males vs. 4% in females.

Key points:
- Evaluate duration and progression of the nodule.
- Investigate compression symptoms and hyper/hyposecretion symptoms.
- Family history assessment for thyroid syndromes.
- Look for neurocutaneous markers (neurofibromas, café-au-lait spots).
- Physical examination should assess:
- Nodule characteristics
- Cervical lymphadenopathy.
Features concerning for malignancy:
- Hard, fixed nodule
- Regional lymphadenopathy.
- Combination features yield a 100% positive predictive value for malignancy.

Initial assessment via Thyroid-stimulating hormone (TSH).
In cases of hypothyroidism, test for:
- Antithyroid antibodies (autoimmune component).
- Calcitonin should only be measured if features suggest medullary carcinoma or MEN 2 syndrome.
- Serum calcium, parathyroid hormone, and urinary metanephrines to assess for MEN 2 patients.

Ultrasonography is critical for nodular disease assessment.
- High-resolution linear probes for better visualization.
- Optimal frequency for thyroid assessment: 7.5–10 MHz.
Characteristics favoring malignancy in nodules include:
1. Size and Composition: Taller than wide; solid vs. cystic.
2. Echogenicity: Hypoechoic nodules (10–20% malignancy risk) vs. hyper/iso-echoic (5–10%).
3. Margins: Irregular (60–70% sensitivity).
4. Calcifications: Microcalcifications (high specificity for papillary carcinoma).
5. Vascularity: Contemporary data suggest lesser importance.
6. Cervical Lymphadenopathy: Abnormal lymph nodes indicate malignancy.

Elastography: Measures stiffness of nodules for better malignancy assessment.
- Strain elastography and acoustic radiation force impulse elastography methods enhance sensitivity.
CEU provides additional diagnostic information.
- Requires large-scale studies for validation.

AI methods enhance diagnostic accuracy; however, need further validation in clinical use.

Nodule assessment variability: No single feature reliably distinguishes malignant from benign. Various classification systems score ultrasound features to stratify risks.
- ACR TIRADS and ATA guidelines position nodules from benign to highly suspicious.

Cross-sectional imaging (CT & MRI) less common for initial evaluation but useful for advanced thyroid cancer.
- Thyroid scintigraphy: Differentiate functioning nodules; hot nodules rarely malignant, cold nodules have a 5–15% malignancy risk.

FNA reserved for nodules suspicious based on prior ultrasound findings, behavior in PET scans.
New changes to Bethesda system include:
- Terminology adjustments and categories to improve clarity.
- Classification impact on surgical decisions.

Liquid biopsy shows promise in evaluating circulating tumor cells and free DNA for malignancy prediction.
Further validation required.

Depends on the nodule's benign, indeterminate, or malignant characterization.
Benign nodules: Regular follow-up unless symptomatic or over 4 cm in size.
Surgery: Hemithyroidectomy for benign solitary nodule; total thyroidectomy for multinodular goiters.
Minimally Invasive Methods: Ethanol injections, thermal ablation, radiofrequency, microwave, and laser ablation approaches recommended for symptomatic, non-surgical candidates.

For indeterminate nodules, factors such as size, patient preference, and test availability guide therapy decisions.
For malignant nodules, surgical interventions are preferred:
- Lobectomy for solitary small tumors.
- Total thyroidectomy for larger, more advanced cases.

Endoscopic and robotic techniques: Improved cosmetic outcomes, less pain, comparable safety to conventional methods.

Need for an individualized approach in managing thyroid nodules. Although malignancy rate is low, careful evaluation through ultrasound, FNA, and risk assessments play essential roles. New molecular tests show potential for refining treatments.