Two cases of pituitary Crooke's cell adenoma without Cushing's disease:: A histologic, immunocytochemical, electron microscopic and in situ hybridization study

Presented herein are the morphologic features of two cases of pituitary Crooke's cell adenoma unassociated with Cushing's disease. Both were removed surgically, one from a 62-yr-old woman and the other from a 37-yr-old man. Crooke's cell adenomas are rare. All previously published cases were associated with clinical and laboratory evidence of Cushing's disease. The two cases presented here are the first that were unaccompanied by adrenocorticotropin (ACTH)-cortisol excess. Crooke's cell adenomas are composed of abnormal corticotrophs containing periodic acid-Schiff- (PAS) negative, ACTH-immunonegative, and keratin-immunoreactive cytoplasmic microfilaments filling large areas of the cytoplasm and displacing other organelles. Adenomatous Crooke's cells express proopiomelanocortin (POMC) mRNA. The question of whether the absence of ACTH-cortisol hypersecretion in our two cases is mediated via functioning glucocorticoid receptors in the adenoma cells or whether other mechanisms are involved remains to be elucidated.