Mucosal ganglioneuromatosis, medullary thyroid carcinoma, and pheochromocytoma: multiple endocrine neoplasia, type 2b.

Multiple endocrine neoplasia, type 2b, is a designation that has been proposed for the combination of medullary thyroid carcinoma, pheochromocytoma, mucosal neuromas, and somatic abnormalities. The neural lesions produce a characteristic diffuse or nodular enlargement of lips, tongue, and buccal mucosa. Microscopically, the lesions are composed of unencapsulated masses of hypertrophied and elongated nerves in which are found rare ganglion cells. The histologic similarity between the oral mucosal lesions and the alimentary tract ganglioneuromatosis in the syndrome suggests that the term ganglioneuromatosis is the most appropriate designation for the oral lesions. The oral lesions signal high risk for two potentially lethal neoplasms--medullary thyroid carcinoma and pheochromocytoma. Thus, patients having the characteristic findings are in urgent need of repeated evaluation of thyroidal C-cell and adrenal medullary function.