Diagnosis of pituitary adenomas on touch preparations assisted by immunocytochemistry

Touch preparations from surgically removed pituitary adenomas were studied by both routine staining and immunocytochemistry for all anterior pituitary hormones. The results were correlated with the histologic, histochemical, immunohistochemical and ultrastructural findings. Several features were recognized, some of them applicable in diagnosing various adenoma types: high cellularity, cell monomorphism, nuclear irregularities and heterogeneity of immunoreactivity, all major diagnostic criteria of pituitary adenoma. The presence of numerous fibrous bodies associated with nuclear pleomorphism, multinucleation and peripheral displacement of nuclei, in association with growth hormone (GH) immunopositivity, represent diagnostic criteria for sparsely granulated GH cell adenoma. The "Golgi" pattern of prolactin (PRL) immunopositivity in conjunction with the small size of cell and nucleus and the presence of microcalcifications represents diagnostic features of PRL-secreting adenoma. Cytoplasmic accumulation of hyaline material in association with peripheral distribution of periodic acid-Schiff stain and adrenocorticotropic hormone immunoreactivity is characteristic of sparsely granulated corticotroph cell adenoma. Knowledge and application of the described features may contribute significantly to the diagnostic approach to pituitary adenomas.