Medullary carcinoma of the thyroid gland.

Out of the discovery of concurrent multiple endocrine neoplasms has evolved the concept of multiple endocrine adenomatosis (MEA1 and MEA2). Medullary carcinoma of the thyroid gland is the most constant facet of MEA2 and is derived from C-cells of the neural crest. These cells, resembling parafollicular cells of lower animals, elaborate calcitonin which acts as a sensitive signal of the presence of the tumor. Ninety per cent of MCT occurs sporadically; in 10% the tumor presents as an atuosomal dominant trait. Other endocrinopathies, especially pheochromocytomas, are present in 70% of cases. The lesions are "cold" on iodine radioisotope scan. On microscopic examination, the appearance of amyloid is characteristic. Regional lymph node metastasis occurs early. The tumor deserves appropriate aggressive management. Surgical therapy should begin early and vigorously with the minimum procedure being total thyroidectomy. Frequent lymph node metastasis speaks for the need for regional neck dissection extended into the superior mediastinum. The search for, and the treatment of, the frequently associated endocrinopathies is essential. Pheochromocytoma must be suspected and eradicated before treatment of the thyroid tumor. A genetic workup should be included.