Medullary carcinoma of the thyroid as a cause of Cushing's syndrome: a case with ectopic adrenocorticotropin secretion characterized by double enzyme immunostaining.
A case of a medullary carcinoma of the thyroid gland that secreted both calcitonin and adrenocorticotropin (ACTH) is reported. The patient was a 32-year-old man who was referred to the Clinical Center of the National Institutes of Health with radiologic evidence of intrathoracic and hepatic masses accompanied by florid Cushing's syndrome. Serum levels of calcitonin and ACTH were elevated. The thoracic and hepatic masses were resected. The histologic findings were typical of medullary carcinoma of the thyroid with extensive metastases to the liver. The neoplasm had a predominantly solid pattern, and the neoplastic cells were either round or spindled, many with cytologic atypia. Immunohistochemical analysis of fixed, paraffin-embedded sections demonstrated chromogranin, calcitonin, and ACTH in the neoplastic cells. The immunostaining for chromogranin was intense in all of the cells, whereas weaker staining for calcitonin and ACTH was present in scattered cells. Electron microscopy revealed sparse secretory granules in the majority of tumor cells; a minority of neoplastic cells contained numerous granules. We further characterized this neoplasm by performing dual immunohistochemical analysis. This technique clearly demonstrated the presence of ACTH and calcitonin within the same neoplastic cells. Thus, the medullary carcinoma of the thyroid in this patient was the source of ectopic ACTH secretion causing Cushing's syndrome. In addition, this report highlights the value of using double immunostaining to localize both the ACTH and calcitonin within the same cells.
Hijazi
Y M
YM
Surgical Pathology Section, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
Nieman
L K
LK
Medeiros
L J
LJ
D000182:ACTH Syndrome, Ectopic / Q000150:complications*; D000328:Adult; D002116:Calcitonin / Q000378:metabolism; D002277:Carcinoma / Q000150:complications* / Q000378:metabolism / Q000473:pathology; D003480:Cushing Syndrome / Q000209:etiology*; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D008854:Microscopy, Electron; D013964:Thyroid Neoplasms / Q000150:complications* / Q000378:metabolism / Q000473:pathology
D002116:Calcitonin