Medullary thyroid carcinoma
- Lesion
A thyroid cancer of the calcitonin-making cells. Some families inherit it through the RET gene, so relatives are tested and operated on early.
What it is
Medullary carcinoma is a neuroendocrine tumour of the parafollicular C cells, which derive from neural crest via the ultimobranchial body. It secretes calcitonin, and its stroma contains amyloid made of calcitonin. Most cases are sporadic, but a substantial minority are familial in MEN2A, MEN2B or familial medullary carcinoma, all caused by germline RET activating mutations.
Structure
- Gross: firm grey-tan, sometimes gritty nodule, often in the upper half of the lobes where C cells live.
- Micro: polygonal to spindle cells in nests, trabeculae or sheets; salt-and-pepper chromatin.
- Acellular amyloid in the stroma.
- Electron microscopy: membrane-bound neurosecretory granules.
- Familial: multifocal C-cell hyperplasia, the precursor lesion.
Markers
- Calcitonin
- CEA
- Chromogranin
- Synaptophysin
- TTF1
- Congo red
Clinical notes
- Neck mass or nodal metastasis; diarrhoea from calcitonin or VIP.
- Serum calcitonin and CEA follow disease after surgery.
- Every patient with medullary carcinoma is offered germline RET testing.
Test yourself
Think of the answer, then tap the question to see it.
What is the amyloid in medullary thyroid carcinoma made of?
Calcitonin (procalcitonin) polypeptides secreted by the tumour cells.
Which precursor lesion is seen in familial medullary carcinoma?
Multicentric C-cell hyperplasia.
Why are RET mutation carriers offered thyroidectomy?
Nearly all will develop medullary carcinoma, which is curable only if removed before it spreads.
Elsewhere in DurgiPedia
- Thyroid follicles, C cells and parathyroid
- Pharyngeal pouches: tonsil, thymus, parathyroids and C cells
- Special stains in diagnosis: Congo red, Prussian blue, PAS, Ziehl–Neelsen, Gram
- Tumour markers: serum and tissue, and what each one is for
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Thyroid Cancer Treatment (PDQ®)–Health Professional Version (National Cancer Institute, 2025); Multiple endocrine neoplasia: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2025).
Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake
Representative model, for educational purposes only.