Should a partial thyroidectomy or a total thyroidectomy be recommended for a patient with a 3.07 cm thyroid nodule and atypia of undetermined significance?

Management of a 3.07 cm Thyroid Nodule with Atypia of Undetermined Significance and NRAS Mutation

A right thyroid lobectomy (partial thyroidectomy) is recommended for this patient with a 3.07 cm TR4 nodule showing atypia of undetermined significance with Hurthle cells and an NRAS mutation. 1, 2

Rationale for Lobectomy vs. Total Thyroidectomy

Patient-Specific Factors Supporting Lobectomy:

• Nodule characteristics: The 3.07 cm right nodule is below the 4 cm threshold that would mandate total thyroidectomy 1
• Molecular profile: The NRAS mutation without high-risk mutations (BRAF, TERT, RET) suggests intermediate risk rather than high-risk disease 3
• Imaging features: Smooth margins and encapsulated appearance on ultrasound are favorable features 2
• Normal thyroid function: TSH, free T4, and free T3 are all within normal ranges 1
• No suspicious lymphadenopathy: Absence of suspicious lymph nodes on ultrasound examination 1

NCCN Guideline Support:

• NCCN guidelines indicate lobectomy is appropriate when all of the following criteria are met:
  • No distant metastases (confirmed in this case)
  • No cervical lymph node metastases (confirmed in this case)
  • No extrathyroidal extension (smooth margins on ultrasound suggest this)
  • Tumor ≤4 cm in diameter (this nodule is 3.07 cm) 1

Left Nodule Considerations:

• The left 1.0-1.2 cm nodule has benign cytology (Bethesda II) and does not require surgical intervention on its own 2

Benefits of Lobectomy vs. Total Thyroidectomy

Advantages of Lobectomy:

• Preserved thyroid function: Patient can maintain normal thyroid function without lifelong hormone replacement 1
• Lower complication risk: Reduced risk of hypoparathyroidism and recurrent laryngeal nerve injury 1
• Adequate for NIFTP or minimally invasive disease: Sufficient treatment for the most likely diagnoses in this case 1
• Option for completion thyroidectomy: Can proceed to total thyroidectomy if final pathology indicates higher risk 4

Disadvantages of Total Thyroidectomy:

• Lifelong hormone replacement: Patient would require thyroid hormone replacement therapy 1
• Higher complication rates: Increased risk of hypoparathyroidism (2.6%) and recurrent laryngeal nerve injury (3%) 1
• Potentially unnecessary for low/intermediate risk disease: May be overtreatment for NIFTP or minimally invasive follicular carcinoma 1

Risk Assessment

Malignancy Risk Factors:

• Nodule size >1.5 cm: The 3.07 cm size increases malignancy risk 5
• Age >45 years: If the patient is over 45, this would further increase malignancy risk 5
• Nuclear atypia with Hurthle cells: Associated with increased malignancy risk 3
• NRAS mutation: Suggests intermediate-to-high probability of cancer or NIFTP 6

Mitigating Factors:

• Absence of high-risk mutations: No BRAF, TERT, or RET mutations 1
• Regular borders on ultrasound: Smooth margins are a more favorable feature 2
• No suspicious lymphadenopathy: Absence of metastatic disease 1

Management Algorithm

1. Proceed with right thyroid lobectomy as the initial surgical approach 1
2. Obtain intraoperative frozen section to guide extent of surgery if available 1
3. Based on final pathology:
   • If NIFTP or minimally invasive follicular carcinoma with negative margins: No further surgery needed 1
   • If invasive carcinoma with adverse features (positive margins, vascular invasion, or extrathyroidal extension): Consider completion thyroidectomy 1, 4
4. Post-lobectomy monitoring:
   • Regular ultrasound surveillance of remaining thyroid lobe 2
   • Thyroid function monitoring 1
   • Consider levothyroxine therapy to keep TSH low or normal 1

Important Considerations

• Surgical expertise: Procedure should be performed by an experienced thyroid surgeon to minimize complications 1
• Pathology review: Final diagnosis requires comprehensive histopathological examination 1
• Patient factors: While not explicitly stated in the case, patient preference, comorbidities, and quality of life considerations should be factored into the final decision 1

Potential Complications to Monitor

• Recurrent laryngeal nerve injury: Risk is lower with lobectomy (1.9%) compared to total thyroidectomy (3%) 1
• Hypoparathyroidism: Risk is significantly lower with lobectomy (0.2%) compared to total thyroidectomy (2.6%) 1
• Need for hormone supplementation: May be necessary even after lobectomy, but at lower doses 1