Familial and Sporadic Medullary Thyroid Carcinoma: Clinical and Immunohistological Findings

We have studied the clinical and thyroid immunohistologicalfeatures of 19 patients with sporadic medullary thyroid carcinomaand 16 patients with the hereditary syndrome multiple endocrineneoplasia 2a (MEN 2a). Both groups were identified by familyscreening using serum calcitonin determinations before and afterpentagastrin stimulation. Pheochromocytoma and hyperparathyroidismwere associated both with multiple endocrine neoplasia 2a andsome cases of sporadic medullary thyroid carcinoma. Hereditarymedullary thyroid carcinoma was invariably associated with C-cellhyperplasia, but C-cell hyperplasia was also associated withsome sporadic tumours. All tumours were positive for calcitoninand carcinoembryonic antigen (by immunohistological staining)(CEA) and most tumours stained for somatostatin. C-cell hyperplasiaalso stained for calcitonin, CEA and somatostatin. We concludethat sporadic and familial medullary thyroid carcinoma cannotalways be discriminated by clinical or immunohistological methods.Family screening is essential in the diagnosis of hereditarymedullary thyroid carcinoma.