 reported cases of a difference disease—the "multiple mucosal neuroma syndrome"—having the physical phenotype of MEN2B, but without variations in the RET gene and without malignancy.MEN2B should be entertained as a diagnosis whenever a person is found to have either medullary thyroid carcinoma or pheochromocytoma.Before DNA testing became available, measurement of serum calcitonin was the most important laboratory test for MEN2B.