Ga-DOTANOC PET/CT done to localize an ectopic adrenocorticotropic hormone-producing tumor revealed metastatic medullary carcinoma of the thyroid as the culprit lesion.
Predicting the development of Cushing's syndrome in medullary thyroid cancer: utility of proopiomelanocortin messenger ribonucleic acid in situ hybridization.
ACTH stains were unrevealing, but proopiomelanocortin mRNA in situ hybridization in MTC tissue and plasma ACTH response to neck dissection confirmed MTC as the source of ectopic ACTH.
It was previously reported a MEN 2A kindred in which the father presented with a rare phenotype consisting of bilateral ACTH-producing pheochromocytoma and medullary thyroid carcinoma.
(1) This first comparison between somatostatin receptor status in vivo and ex vivo in MTC shows a marked positive octreoscan despite absent SSTR 2 expression, and (2) this is the first report of a discrepancy between immunostaining and gene transcription for POMC and CRH.
The length of POMC mRNA in MTCs (present in all 4 metastases investigated but not in 7 primary tumors) and pheochromocytomas is about 100 nucleotides more than pituitary POMC RNA.
In conclusion, 1) hybridization and nucleotide sequence analyses demonstrate that the POMC gene is expressed in MTC metastases; 2) the observed length difference between MTC and pituitary mRNAs suggests differences in expression or processing; 3) no expression of the POMC gene was found in six primary tumors.