Familial and sporadic medullary thyroid carcinoma: clinical and immunohistological findings.

We have studied the clinical and thyroid immunohistological features of 19 patients with sporadic medullary thyroid carcinoma and 16 patients with the hereditary syndrome multiple endocrine neoplasia 2a (MEN 2a). Both groups were identified by family screening using serum calcitonin determinations before and after pentagastrin stimulation. Pheochromocytoma and hyperparathyroidism were associated both with multiple endocrine neoplasia 2a and some cases of sporadic medullary thyroid carcinoma. Hereditary medullary thyroid carcinoma was invariably associated with C-cell hyperplasia, but C-cell hyperplasia was also associated with some sporadic tumours. All tumours were positive for calcitonin and carcinoembryonic antigen (by immunohistological staining) (CEA) and most tumours stained for somatostatin. C-cell hyperplasia also stained for calcitonin, CEA and somatostatin. We conclude that sporadic and familial medullary thyroid carcinoma cannot always be discriminated by clinical or immunohistological methods. Family screening is essential in the diagnosis of hereditary medullary thyroid carcinoma.