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Medullary thyroid cancer

Medullary thyroid carcinoma (MTC) is a sub type of thyroid cancer which accounts for 3.5 - 10% of all thyroid malignancies1. It occurs both sporadically (80%) and as a familial form 4.

It is characterised by consistent production of a hormonal marker, calcitonin, calcification of both primary and metastatic sites, and association with other endocrine neoplasms. Metastatic involvement may be seen in up to 50% at the time of presentation 4.

Epidemiology

In non familial cases it typically peaks in the 3rd to 4th decades.

Pathology

Thought to arise from parafollicular C cells of the thyroid 4. Amyloid components may be seen on histology.

Associations

When familial, it is seen as a component of multiple endocrine neoplasia type II (MEN-II) syndromes (both MEN IIa and MEN IIb) . Other associations include

Radiographic features

Ultrasound

Punctate high echogenic foci resembling calcification may be seen both within the primary thyroid lesion as well as metastatic regional lymph nodes 3 and distant metastatic sites. Involved lymph nodes typically calcify.

CT

Both primary metastatic lesions usually have irregular dense calcific foci within 1.

In the chest, bullae formation and pulmonary fibrosis might happen as a result of a desmoplastic reaction.

Scintigraphy

Usually not very sensitive 4 . Lesions do not concentrate radioactive iodine since the tumour does not arise from thyroid follicular cells. It has been shown to concentrate Thallium-201. 5

Treatment and prognosis

Total thyroidectomy and neck dissection is a consideration. Prognosis in general tends to be worse than papillary and follicular thyroid cancer sub types 1.  

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