Immunohistochemical localization of keratin in craniopharyngiomas and squamous cell nests of the human pituitary.

To identify keratin, the immunoperoxidase technique was performed on 41 nontumourous pituitaries, 14 pituitary adenomas composed of different cell types and 15 craniopharyngiomas. No keratin was demonstrated in adenohypophysial cells, neurohypophysis or hypophysial vessels, however, it was occasionally identified in the pairs intermedia within cells lining cystic structures. Crooke's hyaline material and all pituitary adenomas were negative for keratin. The epithelial portions of craniopharyngiomas exhibited positive keratin immunostaining, as did squamous cell nests, which are frequently found in hypophysial stalk. Immunostaining for keratin can effectively be used in the differential diagnosis of pituitary tumours and may prove valuable in the investigation of histogenesis and embryology.