Medullary thyroid carcinoma identified by cell-free translation of tumor messenger ribonucleic acid in a patient with a neck mass and the syndrome of ectopic adrenocorticotropin.

We report a patient who presented with a lateral neck mass and Cushing's syndrome secondary to the ectopic production of ACTH. The initial diagnosis was a nonchromaffin paraganglioma based on conventional light and electron microscopic studies. However, during this patient's hospital course, we determined that mRNA extracted from the tumor directed the translation of a calcitonin precursor in a cell-free system. This finding led to a consideration of the diagnosis of medullary thyroid carcinoma, which was then confirmed by further endocrine and histological evaluations. This is a report of the identification of a tumor type using techniques of molecular biology.