medullary thyroid cancer
Meaning of medullary thyroid cancer: The one thyroid cancer arising from a different cell type entirely, and the one most likely to run in families.
Definition of medullary thyroid cancer
Medullary thyroid cancer is an uncommon thyroid cancer that begins in the parafollicular C cells rather than in the follicular cells that make thyroid hormone. Those C cells release calcitonin, so the amount of calcitonin in blood works as a marker of the tumor. A substantial share of cases are inherited through a change in the RET gene.
How does it differ from the common thyroid cancers?
| Feature | Papillary and follicular | Medullary |
|---|---|---|
| Cell of origin | Follicular cells making thyroid hormone | Parafollicular C cells |
| Blood marker | Thyroglobulin | Calcitonin |
| Radioactive iodine | Taken up, so useful | Not taken up, so of no use |
| Inherited forms | Uncommon | A substantial share |
The difference in cell type drives everything else. Because C cells do not absorb iodine, the radioactive iodine treatment that underpins management of papillary thyroid cancer has no effect here, and the completeness of surgery carries correspondingly more weight.
What does calcitonin do?
C cells release calcitonin, a hormone that lowers blood calcium by slowing the cells which break bone down. Its role in humans is minor, and people whose thyroid has been removed manage without it. Its value here is as a marker. The level tracks the amount of tumor present, falls after successful surgery, and a rise afterward signals recurrence, often long before anything appears on a scan. A second substance, carcinoembryonic antigen, is followed alongside it.
Why does it run in families?
Inherited cases arise from a change in the RET gene, which codes for a receptor driving cell growth. A single altered copy is enough, and each child of an affected parent has an even chance of inheriting it. The change may occur alone, as familial medullary thyroid cancer, or as part of a syndrome that also brings tumors of the adrenal gland and overactive parathyroid glands. Genetic testing of relatives identifies carriers before any tumor develops, and the age at which disease appears varies with the exact change involved.
How is it treated?
Removing the whole thyroid, together with the lymph nodes of the central neck, is the mainstay, since these tumors reach nodes early. Thyroid hormone is then taken for life, as after any complete removal, though here it replaces rather than suppresses. Where disease persists or returns, drugs that block the RET pathway and related enzymes are available. Calcitonin measurement guides follow-up more sensitively than imaging does.
Also known as
Used in a sentence
A raised calcitonin level prompted investigation that confirmed medullary thyroid cancer.
Good to know
Medullary thyroid cancer does not take up radioactive iodine, so the treatment used for the common thyroid cancers has no role and complete surgery matters more.
Word origin
Where “medullary thyroid cancer” comes from
Medullary comes from the Latin medulla, meaning marrow or inner part, describing where these cells sit within the gland.