Predicting the development of cushing's syndrome in medullary thyroid cancer : Utility of proopiomelanocortin messenger ribonucleic acid in situ hybridization

Objective: To determine the ability to predict the development of Cushing's syndrome (CS) by immunostaining prior to its clinical recognition. Design: In the current report, we demonstrated that a medullary thyroid carcinoma (MTC) patient had the ability to develop CS several years before its clinical recognition. Special stains on tumor tissue confirmed the presence of ectopic adrenocorticotropic hormone (ACTH) 3 years before his clinical presentation of CS. Subsequently, we identified eight MTC patients and reviewed their records to determine whether there was clinical or laboratory evidence of CS. Tissue blocks were obtained from the primary tumor and metastasic lesions for ACTH staining and for proopiomelanocortin messenger ribonucleic acid (POMC mRNA) in situ hybridization. Chromogranin A staining was also performed. Main outcome: ACTH staining did not detect ectopic ACTH. However, measuring ACTH precursor (POMC mRNA) by in situ hybridization confirmed the diagnosis, which preceded the patient's clin...