Medullary thyroid cancer (MTC) comprises 3% to 4% of all thyroid cancers. These tumors usually present as a mass in the neck or thyroid, often associated with lymphadenopathy, or they may be diagnosed through screening family members. MTC can also be diagnosed by fine-needle aspiration biopsy. Cytology typically reveals hypercellular tumors with spindle-shaped cells and poor adhesion.
The overall survival of patients with MTC is 86% at 5 years and 65% at 10 years. Poor prognostic factors include advanced age, advanced stage, prior neck surgery, and associated multiple endocrine neoplasia (MEN) 2B.[2,3,4]
By Darci Picoult
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Approximately 25% of reported cases of MTC are familial. Familial MTC syndromes include MEN 2A, which is the most common; MEN 2B; and familial non-MEN syndromes. (Refer to the PDQ summary on Genetics of Endocrine and Neuroendocrine Neoplasias for more information.) Any patient with a familial variant should be screened for other associated endocrine tumors, particularly parathyroid hyperplasia and pheochromocytoma. MTC can secrete calcitonin and other peptide substances. Determining the level of calcitonin is useful for diagnostic purposes and for following the results of treatment.
Family members should be screened for calcitonin elevation and/or for the RET proto-oncogene mutation to identify other individuals at risk for developing familial MTC. All patients with MTC (whether familial or sporadic) should be tested for RET mutations, and if they are positive, family members should also be tested. Whereas modest elevation of calcitonin may lead to a false-positive diagnosis of medullary carcinoma, DNA testing for the RET mutation is the optimal approach. Family members who are gene carriers should undergo prophylactic thyroidectomy at an early age.[5,6]
Patients with MTC should be treated with a total thyroidectomy, unless there is evidence of distant metastasis. In patients with clinically palpable MTC, the incidence of microscopically positive nodes is more than 75%; routine central and bilateral modified neck dissections have been recommended. When cancer is confined to the thyroid gland, the prognosis is excellent.