A Case of Nonfunctioning Pituitary Adenoma Resembling So-called Silent Corticotroph Adenoma.

It has been indicated that some subsets of clinically nonfunctioning pituitary adenoma exhibit immunohistochemical and ultrastructural features of somatotroph or corticotroph cells, which are described as silent somatotroph and corticotroph adenomas, respectively. We here describe a 70-year-old woman with nonfunctioning pituitary adenoma presenting with visual disturbance. None of the pituitary hormones show abnormal finding. Magnetic resonance imaging study revealed a pituitary tumor which developed inferiorly into the sphenoidal sinus. Tumor resection was performed by a transsphenoidal approach, and resulted in a partial resection of the tumor. The specimen indicated chromophobic adenoma. Immunohistochemical examination revealed a characteristic distribution pattern of cytokeratin staining for ACTH cell adenoma, although immunostaining for ACTH was only weakly positive. After the operation, only ACTH secretion was impaired, requiring replacement therapy with glucocorticoid. Bromocriptine was administered in order to prevent the recurrence of the tumor. It remains to be elucidated whether the present case could be classified as silent corticotroph adenoma, which was origially indicated to have aggressive characteristics, i.e. progressive visual defect, high incidence of infarction and frequent recurrence.