# Medullary Thyroid Cancer

URL: https://thethyroidologist.com/conditions/medullary-thyroid-cancer/
Section: Conditions
Last medically reviewed: 2025-11-01

> Medullary thyroid cancer — arises from parafollicular cells, can be hereditary (MEN2). Calcitonin testing, genetic screening and total thyroidectomy.

Medullary thyroid cancer (MTC) develops from the parafollicular C cells of the thyroid, which produce calcitonin. It accounts for about 3–4% of thyroid cancers and behaves differently from the common differentiated types.
A key feature: roughly a quarter of cases are hereditary, linked to RET gene mutations, often as part of multiple endocrine neoplasia type 2 (MEN2).

## Sporadic vs hereditary

Sporadic MTC occurs without family history. Hereditary MTC occurs in MEN2A and MEN2B syndromes or as familial medullary thyroid cancer (FMTC), all caused by RET proto-oncogene mutations.
Because hereditary forms can be aggressive — especially MEN2B — genetic testing of the patient and at-risk relatives is essential and guides the timing of preventive surgery.

## Diagnosis

A thyroid nodule with elevated calcitonin on blood testing raises suspicion. FNAC may show amyloid or medullary features, but calcitonin and CEA levels are the key tumour markers. Neck ultrasound and sometimes CT assess spread.
All confirmed MTC patients should undergo RET genetic testing.

## Treatment

Total thyroidectomy with central neck lymph node dissection is standard for MTC, since the C cells are distributed throughout the gland and cannot be selectively removed. For hereditary cases, surgery timing is driven by the specific RET mutation risk level.
Radioactive iodine is not effective in MTC (C cells do not take up iodine). External beam radiation may be used for unresectable or residual disease; targeted therapies (tyrosine kinase inhibitors) treat advanced disease. Lifelong calcitonin and CEA surveillance tracks recurrence.

## Frequently asked questions

### Is medullary thyroid cancer hereditary?

Yes, about 25% of cases are hereditary, caused by RET gene mutations — sometimes isolated, sometimes part of MEN2 syndrome. Genetic testing guides treatment and screening of relatives.

### Why doesn’t radioactive iodine work for MTC?

Radioactive iodine works only on follicular cells that express the sodium-iodide symporter. Medullary cancer arises from C cells, which lack this mechanism.

### What is the follow-up after MTC surgery?

Calcitonin and CEA levels are monitored lifelong — a rising calcitonin is the earliest sign of recurrence. Neck ultrasound and imaging follow as indicated.

## Disclaimer

The content on this website is for general educational purposes only and does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional about your specific condition.

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