MEDULLARY
THYROID CANCER (MTC), AN AGGRESSIVE THYROID MALIGNANCY-HOW FREQUENT IS IT AND
WHAT’S ITS ETIOLOGY
MTC
constitutes 2 – 5 % of all thyroid cancers. Most (75 – 80 %) MTCs are sporadic,
and the remainder are familial as a particular manifestation of multiple
endocrine neoplasia syndrome (type 2A and 2B) and familial medullary thyroid
cancer (FMTC). RET mutations in neural crest tissue in the thyroid can lead to
MTC development. Germline RET mutations are associated with the hereditary MTC
(in MEN2 syndrome and in FMTC), while about 40 – 50 % of sporadic MTC have
acquired RET mutations. Sporadic MTC has a peak incidence in the 5th or 6th
decade of life, whereas hereditary MTC peaks around the 2nd or 3rd decade.
While sporadic MTC is typically unilateral, hereditary MTC is usually
multicentric and bilateral, often involving the upper part of both lobes, since
C-cells are mainly located in the upper poles of the thyroid parenchyma. MTC is
associated with a more aggressive biological behavior compared to the much more
common differentiated thyroid cancer (papillary / follicular). However, in
early stages prognosis could be excellent, but aggravates in more advanced
disease (10-yr survival for stages I, II, III and IV; 99 %, 93 %, 71 % and 21
%, respectively). Appropriate radical surgery is of key importance to achieve
optimal outcome.
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