[Prophylactic thyroidectomy in carriers of RET oncogene mutation carriers]

Medullary thyroid cancer may be inherited dominantly. Germline mutations in the RET oncogene which code for a receptor tyrosine kinase cause MEN2. Thyroidectomy is recommended in family members who carry a mutation.

We have thyroidectomized four children from three families, 12, 10, 7 and 6 years old, because of germline mutations.

The 12-year-old had developed a minimal medullary cancer with microscopic lymph node metastases; the others showed variable degrees of C-cell hyperplasia. The mutations were located on exon 10 (C620F) in the two patients from one family, on exon 11 (C634R) in the second family and on exon 14 (V804M) in the third family. In the families with the codon 620 and codon 634 mutations, only medullary thyroid cancer has been diagnosed. In the family with the codon 804 mutation, the index patient has been operated for a pheochromocytoma. The longterm clinical course seems more favorable in the family with the codon 620 mutation than in the two other families. With knowledge of the family mutations, we found that two out of nine family members we previously have thyroidectomized following calcitonin testing did not carry the family mutation.

Genetic diagnostic is a safe and reliable predictive test for familial medullary thyroid cancer and should be carried out in any individual with this cancer. Thyroidectomy is recommended in gene carriers at the age of six.