Unilateral surgery supported by germline RET oncogene mutation analysis inpatients with sporadic medullary thyroid carcinoma

Compared to hereditary medullary thyroid carcinoma (MTC), sporadic MTC tend s to be unicentric and confined to one lobe. Patients with sporadic MTC usu ally undergo total thyroidectomy because of a possible hereditary or bilate ral process. We evaluated the usefulness of germline RET oncogene mutation analysis in surgery for apparently sporadic MTC and performed unilateral su rgery on patients without detectable mutation. In 36 patients with a preope rative diagnosis of apparently sporadic MTC, we performed germline RET onco gene mutation analyses: before surgery in 8 recent patients and after surge ry in 28 who had been treated before 1996. Of the latter, 5 had bilateral M TC. DNA samples were extracted from their peripheral blood, and the polymer ase chain reaction products of the RET proto-oncogene were analyzed using s ingle-strand conformation polymorphism analysis and the direct sequencing m ethods. Before 1996 we often performed total thyroidectomy but changed to h emithyroidectomy thereafter, except in one patient with associated Graves' ophthalmopathy. Our minimal standard practice included systematic central a nd ipsilateral neck dissection. The outcome was assessed in terms of gastri n- and calcium-stimulated plasma calcitonin levels. Germline RET mutations mere found in six patients. Five of these patients had bilateral MTC, where as all 30 patients without mutation had unilateral disease. Hemithyroidecto my in seven of our recent patients resulted in normalization of plasma calc itonin levels in all, although four were found to have microscopic lymph no de involvement. In conclusion, hemithyroidectomy with systematic central an d ipsilateral neck dissection is an appropriate procedure for patients with sporadic MTC without detectable germline RET mutations.