Pituitary corticotroph adenoma with crooke's hyalinization

The diagnosis of pituitary corticotroph adenoma relies on the demonstration of a loss of the normal feedback control of adrenocorticotropic hormone (ACTH) biosynthesis by cortisol. The marked variability in the degree of ACTH suppression by glucocorticoids in these tumors, however, greatly enhances the difficulty in distinguishing Cushing's disease from other syndromes of glucocorticoid excess. To illustrate this variability, we describe the clinical, biochemical, and morphological characteristics of a pituitary corticotroph adenoma in a 63-year-old woman, who presented with symptoms of a sellar mass but did not initially have florid Cushing's disease. Light and electron microscopy of the pituitary tumor showed a corticotroph adenoma with Crooke's hyalinization of the tumor cells, characterized by the accumulation of keratin immunoreactive microfilaments similar to those observed in normal corticotrophs in the presence of excess glucocorticoids. This case illustrates an unusual clinical presentation that may be associated with pituitary corticotroph adenoma showing Crooke's hyalinization.