Immunohistological study of Crooke's cells.

By immunohistochemical methods, 28 postmortem pituitary glands with unequivocal Crooke's hyaline change were examined to identify the hyaline material. Crooke's hyaline was positive for 55-57 kilodalton (KD) cytokeratin (CK) but negative for 68 KD CK, vimentin, desmin, neurofilament and glial fibrillary acidic protein. Involucrin, a new marker for keratinocyte differentiation, could also not be demonstrated. It was concluded that Crooke's hyaline was an abnormally accumulated CK which is a normal constituent of the ACTH cell.