Medullary Thyroid Carcinoma Surgery
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Direct answer
Parafollicular C cells — neural-crest-derived, calcitonin-secreting, scattered in the lateral upper two-thirds of the thyroid — give rise to medullary thyroid carcinoma, about 5–10% of thyroid malignancies, of which roughly a quarter are familial (MEN2). The tumour deposits amyloid stroma, expresses calcitonin and CEA, and demands RET germline testing in every new case. Surgery is total thyroidectomy with at least central-compartment (level VI) node dissection, lateral neck dissection when nodes are involved — and neither radioiodine nor TSH suppression has any role, because C cells neither trap iodine nor respond to TSH.
What you must remember
- Origin: parafollicular C cells of neural crest origin; familial tumours are bilateral and multicentric against a background of C-cell hyperplasia, sporadic tumours usually unifocal.
- Markers: calcitonin for diagnosis and follow-up, CEA for burden and prognosis (a rising CEA with plateauing calcitonin signals dedifferentiation); stimulated calcitonin testing is used in some centres.
- Histology: sheets of polygonal cells with characteristic amyloid stroma (Congo red positive, apple-green birefringence); confirmed by calcitonin and chromogranin immunostaining.
- Clinical hints: firm thyroid mass with early nodal spread; diarrhoea and flushing from secretory products in advanced disease.
- Every patient with medullary carcinoma gets RET germline testing — a positive result triggers family cascade testing and prophylactic thyroidectomy planning in affected children.
- Operative standard: total thyroidectomy with routine central compartment (level VI) dissection; therapeutic lateral compartment dissection (levels II–V on the involved side) for nodal disease; more extensive prophylactic lateral dissection is debated for raised calcitonin.
- Before thyroidectomy in familial disease: screen for phaeochromocytoma (metanephrines) and hyperparathyroidism (calcium, PTH) — the adrenal comes first if both are present.
- Postoperative follow-up is calcitonin and CEA; persistent elevation drives localisation with ultrasound, CT, and somatostatin-receptor or other functional imaging, and re-operation if disease is localised and resectable.
- Advanced disease: tyrosine kinase inhibitors (vandetanib, cabozantinib) for progressive metastatic medullary cancer; external beam radiotherapy has selected roles for residual or bone disease.
- The negative statement examiners reward: no radioiodine ablation, no TSH suppression — adjuvant tools of differentiated thyroid cancer that are useless here.
From nodule to operation
A 45-year-old presents with a hard left thyroid nodule and a palpable level III node. FNAC reports medullary carcinoma — amyloid-like stroma with calcitonin immunostain — and serum calcitonin is markedly elevated. Work-up runs on two tracks: staging (neck ultrasound, chest and abdominal CT) and genetics (RET germline testing, returning negative — sporadic disease, no cascade testing).
RET negative and disease confined to the neck, he undergoes total thyroidectomy with central compartment dissection and left lateral functional neck dissection. Postoperative calcitonin falls to undetectable — biochemical cure — and surveillance with calcitonin and CEA proceeds at lengthening intervals. Had calcitonin remained detectable, the search for residual disease would begin after an appropriate interval, with re-operation reserved for structurally identifiable, resectable disease; blind re-exploration for a number alone has fallen out of favour.
Had his RET test been positive, the picture changes for the whole family: children testing positive for his mutation are scheduled for prophylactic thyroidectomy timed to codon risk, and every carrier is screened lifelong for phaeochromocytoma before any operation and for hyperparathyroidism.
Where students slip
The reflex that costs marks is treating this as differentiated thyroid cancer: answering "total thyroidectomy with radioiodine ablation and suppressive levothyroxine" ignores C-cell biology — medullary carcinoma does not take up iodine and is not TSH-dependent, so both adjuvants are futile. The second slip is the missed diagnosis: diarrhoea with a thyroid nodule, or a nodule in a patient with a family history of "thyroid cancer and adrenal problems", should prompt calcitonin and RET thinking rather than the papillary-cancer algorithm. The third is anatomical parsimony — offering thyroidectomy alone without central compartment dissection, when nodal micrometastasis is so frequent that the central clearance is part of the primary operation.
Frequently asked questions
From which cells does medullary thyroid carcinoma arise?
Parafollicular C cells of neural crest origin, which secrete calcitonin; familial cases arise on a background of multifocal C-cell hyperplasia.
Which tumour markers diagnose and follow medullary carcinoma?
Calcitonin for diagnosis, residual disease and recurrence; CEA for tumour burden and prognosis — a rising CEA with stable calcitonin suggests dedifferentiation.
What is the standard surgical procedure?
Total thyroidectomy with routine central compartment (level VI) lymph node dissection, adding lateral compartment dissection on sides with clinically or radiologically involved nodes.
Why is RET testing done in every new case?
About a quarter are hereditary (MEN2); identifying a germline RET mutation triggers family cascade testing, prophylactic thyroidectomy in gene-positive children, and lifelong screening for phaeochromocytoma and hyperparathyroidism.
Why do radioiodine and TSH suppression have no role?
C cells do not express the sodium-iodide symporter or TSH receptors, so neither ablation nor suppression influences the cancer — management is surgical, with kinase inhibitors for advanced disease.
Which drugs are used for progressive metastatic disease?
The tyrosine kinase inhibitors vandetanib and cabozantinib, approved for progressive, unresectable or metastatic medullary thyroid carcinoma.