What is the management and treatment approach for a sudden thyroid mass, including necessary labs and medications?

Management of Sudden Thyroid Mass

A sudden thyroid mass requires immediate evaluation with thyroid ultrasound and fine-needle aspiration cytology (FNAC) for nodules ≥10 mm to determine malignancy risk, followed by measurement of serum TSH, and if malignant or suspicious, total thyroidectomy is the primary treatment. 1

Initial Diagnostic Workup

Laboratory Testing

• Measure serum TSH as the first-line laboratory test to assess thyroid function 2, 3
• If TSH is low or suppressed, obtain free thyroxine (FT4) levels and consider thyroid radionuclide scan 1, 2
• If TSH is elevated, measure thyroid peroxidase antibody 2
• For suspected medullary thyroid cancer (MTC), obtain basal serum calcitonin, CEA, calcium, and plasma or 24-hour urine metanephrines/normetanephrines before surgery 1

Imaging Studies

• Perform thyroid ultrasound on all patients with a palpable thyroid nodule to characterize the mass and assess malignancy risk 1, 2
• Ultrasound features guide the decision for biopsy, with high-risk features including marked hypoechogenicity, microcalcifications, irregular margins, and increased vascularity 1, 3
• Radionuclide scanning is only indicated if TSH is low or suppressed, not as routine screening 2, 3

Fine-Needle Aspiration Biopsy

• Perform ultrasound-guided FNA for nodules ≥10 mm 1, 2
• For nodules <10 mm, FNA is only indicated if clinical features or ultrasound characteristics are highly suspicious for malignancy 1, 2
• If initial FNA is inadequate, repeat the procedure 1, 2
• Cytology results should be interpreted by an experienced pathologist 2

Management Based on Diagnosis

Differentiated Thyroid Cancer (Papillary or Follicular)

Surgical Management:

• Total or near-total thyroidectomy is the initial treatment for confirmed or suspected differentiated thyroid cancer 1
• Less extensive surgery may be acceptable only for unifocal, small, intrathyroidal tumors of favorable histology (classical papillary or follicular variant) discovered incidentally after surgery for benign disease 1
• Use established staging systems (AJCC, ATA, or ETA) immediately after surgery for risk stratification 1

Post-Surgical Treatment:

• Radioiodine (¹³¹I) ablation is indicated for high-risk patients to eliminate remnant thyroid tissue and microscopic residual tumor 1
• Radioiodine is NOT indicated for low-risk patients 1
• For intermediate-risk patients, the decision must be individualized based on specific tumor characteristics 1

Thyroid Hormone Therapy:

• Initiate levothyroxine immediately post-surgery for both replacement and TSH suppression 1, 4
• TSH suppressive therapy with levothyroxine benefits high-risk thyroid cancer patients by reducing growth stimulus on tumor cells 1
• Check thyroid function tests (FT3, FT4, TSH) at 2-3 months post-treatment to verify adequate suppression 1
• Administer levothyroxine on an empty stomach, 30-60 minutes before breakfast with a full glass of water 4
• Avoid concurrent administration with calcium, iron supplements, or antacids (separate by at least 4 hours) 4

Medullary Thyroid Cancer

Pre-Operative Evaluation:

• All patients require staging workup including basal serum calcitonin, CEA, calcium, and metanephrine testing to exclude pheochromocytoma (especially in MEN 2 syndromes) 1
• If pheochromocytoma is present, it must be removed first with appropriate α-adrenergic blockade (phenoxybenzamine) to prevent hypertensive crisis 1

Surgical Approach:

• Total thyroidectomy with bilateral prophylactic central lymph-node dissection (level VI) for tumors ≥1 cm or bilateral disease 1
• Lateral neck dissection reserved for patients with positive preoperative imaging 1
• For tumors <1 cm with unilateral disease, total thyroidectomy is recommended with consideration of neck dissection 1

Post-Operative Management:

• Replacement levothyroxine to maintain TSH in the normal range (NOT suppressed, as C cells lack TSH receptors) 1
• Monitor serum calcitonin and CEA levels as primary surveillance markers 1
• If post-operative calcitonin is undetectable after provocative testing, repeat every 6 months for 2-3 years, then annually 1
• For calcitonin <150 pg/mL, limit surveillance to neck ultrasound 1
• For calcitonin >150 pg/mL, screen for distant metastases 1

Anaplastic Thyroid Cancer

• Anaplastic thyroid cancer is uniformly stage IV disease with extremely poor prognosis (mean survival <6 months) 1
• Surgery is indicated only for local control in resectable lesions 1
• Chemotherapy (doxorubicin alone or with cisplatin) has disappointing results with <20% response rates 1
• External beam radiotherapy is used palliatively 1
• Enrollment in clinical trials should be strongly encouraged 1

Follow-Up Protocol

For Differentiated Thyroid Cancer

• At 6-12 months post-treatment: physical examination, neck ultrasound, and basal plus rhTSH-stimulated serum thyroglobulin measurement with or without diagnostic whole-body scan 1
• For patients considered disease-free: annual physical examination, basal serum thyroglobulin on levothyroxine therapy, and neck ultrasound 1

For Recurrent Disease

• Loco-regional recurrence: combination of surgery and radioiodine therapy, supplemented by external beam radiotherapy if surgery is incomplete or radioiodine uptake is absent 1
• Distant metastases: best outcomes with radioiodine-avid, small lung metastases; otherwise only palliation is feasible 1
• Conventional chemotherapy is not indicated for recurrent differentiated thyroid cancer 1

Critical Pitfalls to Avoid

• Do NOT order radionuclide scans or extensive imaging before endocrinology consultation as these are expensive, delay diagnosis, and rarely change management 5
• Do NOT perform FNA on nodules <10 mm unless highly suspicious features are present, as this can lead to overdiagnosis of clinically insignificant cancers 1, 2
• Do NOT administer iodine before thionamides in thyroid storm, as this can worsen thyrotoxicosis 6
• Do NOT suppress TSH in medullary thyroid cancer patients, as C cells lack TSH receptors and suppression provides no benefit 1
• Do NOT use levothyroxine for weight loss in patients without hypothyroidism 4
• Monitor for agranulocytosis with thionamide therapy and cardiac complications including heart failure 6

Special Considerations for Benign Nodules

• Benign nodules on FNA require follow-up surveillance rather than immediate surgery 1, 2
• Large symptomatic goiters may be treated surgically or with radioiodine 2
• Percutaneous ethanol injection is useful for cystic thyroid lesions 2