Medullary carcinoma of the thyroid

Answer: c



Medullary carcinoma of the thyroid (MCT) accounts for about 7% of all malignant tumors of the thyroid. It is familial in 20% to 30% of all cases and its secretion of a biologic marker (calcitonin) allows detection of its presence with the tumor is too small to palpate. MCT appears in three clinical settings. The first is a sporadic tumor, usually in patients 30 years or older. Second, MCT occurs as a component of the MEN IIa syndrome with or without adrenal medullary disease (pheochromocytoma) or hyperparathyroidism. A family history of thyroid carcinoma with or without pheochromocytoma is invariably present. MCT in the MEN IIa syndrome is always bilateral and multicentric and arises from C-cell hyperplasia. MCT usually does not develop before age 12 and is almost always clinically apparent before age 30.

Lastly, MCT is found as a component of the MEN IIb syndrome without or without bilateral adrenal medullary disease and always with the facies and autonomic nervous system dysplasia expressed as ganglioneuromatosis from the lips to the anus. These patients often have a marfanoid habitus and skeletal deformities as well. The MEN IIb syndrome occurs as a sporadic mutation, but its familial occurrence is becoming more common because patients are surviving now long enough to reproduce. MCT or its precursor, C-cell hyperplasia, develops by age 2 in MEN IIb and is always bilateral and multicentric. As a result of its early appearance and late detection, the disease has usually been more advanced when treatment has been instituted. Minimal treatment of MCT is total thyroidectomy. The overall prognosis for 10-year survival is approximately 50%, although the tumor growth rate in individual patients has shown great variability. Patients with the MEN IIb disease require total thyroidectomy as soon as the syndrome is recognized, preferably by the age of 2 years. In familial cases, the characteristic findings are sufficient even without calcitonin testing to justify operation. If the diagnosis is not made until adolescence or later, both central compartment and lateral node involvement require neck dissection for definitive treatment.

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