GENETIC
TESTING FOR SPORADIC MEDULLARY THYROID CANCER- IS IT INDICATED?
Germline RET testing is recommended for all patients
with apparently sporadic medullary thyroid cancer (MTC). This testing should
initially include sequencing of exons 10, 11 and 13 – 16 of the RET gene. Sequence analysis of the
remaining exons in the RET gene should be considered for patients with clinical
findings indicating the presence of hereditary MTC who do not exhibit mutations
in exons 10, 11 or 13 – 16. Interestingly, a small but significant percentage (~
7 %) of patients with presumed sporadic MTC have germline RET mutations. About three quarters of the familial MTC have no
family history. Approximately 60 % of patients with sporadic MTC have somatic
(acquired) RET mutations which are
present only with the neoplastic cells; for this reason, these mutations can’t
be detected using standard genetic testing (for example analysis of leukocyte
DNA). Acquired RET mutations are usually associated with worse prognosis (increased
incidence of lymph node metastases, recurrent disease, lower survival etc.).
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