Management of Medullary Thyroid Carcinoma Contained in the Thyroid
For medullary thyroid carcinoma (MTC) contained within the thyroid gland without distant metastases, perform total thyroidectomy with bilateral central neck dissection (levels VI) as the definitive surgical treatment. 1
Preoperative Workup
Before surgery, obtain the following essential tests:
- Serum calcitonin and CEA levels to establish baseline tumor markers 1, 2
- Neck ultrasound to map disease extent and identify lymph node involvement 1
- Germline RET mutation testing for all patients with MTC, as up to 10% of apparently sporadic cases harbor hereditary mutations 1
- Serum calcium and plasma/24-hour urine metanephrines/normetanephrines to exclude pheochromocytoma, particularly if hereditary MTC is suspected 3
Surgical Approach Based on Calcitonin Levels
The extent of lymph node dissection should be guided by preoperative calcitonin levels and ultrasound findings 1:
- Calcitonin <20 pg/mL: Total thyroidectomy alone may be considered if ultrasound is negative for lymph nodes 1
- Calcitonin 20-200 pg/mL: Total thyroidectomy with bilateral central neck dissection (levels VI) 1
- Calcitonin >200 pg/mL: Total thyroidectomy with bilateral central neck dissection plus bilateral lateral neck dissection (levels IIA-III-IV) 1
- Ultrasound-positive lymph nodes: Perform therapeutic neck dissection of involved compartments regardless of calcitonin level 1
Critical Surgical Principles
Perform compartmental-oriented lymph node dissection rather than "berry-picking" individual nodes, as systematic removal of entire nodal basins improves biochemical cure rates to >80% in appropriately selected patients 4, 5. The goal is complete surgical resection with curative intent, as MTC does not respond to radioiodine therapy and is relatively radioresistant 4, 6.
Postoperative Management
Do NOT use TSH suppression therapy in MTC patients, as C cells lack TSH receptors and suppression provides no benefit 2, 3. Levothyroxine should only be used for thyroid hormone replacement to maintain TSH in the normal range 2.
Obtain postoperative calcitonin and CEA levels at 2-3 months after surgery 2:
- Undetectable basal calcitonin: Indicates excellent prognosis with very low likelihood of residual disease 1
- Detectable calcitonin: Calculate doubling times from sequential measurements every 6-12 months, as these predict disease aggressiveness and guide further management 2, 7
Follow-Up Imaging
For patients with detectable postoperative calcitonin 1:
- Calcitonin <150 pg/mL: Neck ultrasound every 6-12 months 1
- Calcitonin ≥150 pg/mL: Contrast-enhanced CT of neck, chest, and abdomen to evaluate for distant metastases 1, 2
- Rapidly rising calcitonin or CEA: Consider FDG-PET/CT if calcitonin >1,000 pg/mL or doubling time <12 months 1
Key Pitfalls to Avoid
- Never perform lobectomy alone for MTC unless postoperative calcitonin is undetectable, neck ultrasound is normal, and no germline RET mutation is found 1
- Avoid inadequate initial surgery, as reoperation carries higher morbidity and lower cure rates 4
- Do not delay genetic testing, as 25% of MTC cases are hereditary and family screening is essential 1
- Never use radioiodine therapy for MTC, as these tumors do not concentrate iodine 2, 3, 4