NULL-CELL ADENOMAS, ONCOCYTOMAS, AND GONADOTROPH ADENOMAS OF THE HUMAN PITUITARY - AN IMMUNOCYTOCHEMICAL AND ULTRASTRUCTURAL ANALYSIS OF 300 CASES

The immunocytochemical profile of 300 clinically nonsecreting pituitary adenomas was investigated. All tumors were diagnosed, classified, and separated into null cell adenomas, oncocytomas, and gonadotroph adenomas according to their ultrastructural morphology. The immunocytochemical analysis was based on the semiquantitative proportional estimates of positive cells immunostained for all known peptide and glycoprotein pituitary hormones including alpha-subunit. The majority of tumors (87%) were to some extent immunopositive for various hormones. Glycoprotein hormones were most frequently encountered. Usually, particularly in males, more than one subunit was present in the same tumor. In 97 tumors (32%) more than 25% of adenoma cells were immunoreactive for glycoprotein hormones. Fifty-five tumors (18%) contained occasional cells immunopositive for growth hormone (GH), prolactin (PRL), and adenocorticotropin (ACTH) in addition to glycoprotein hormones. Given the significant proportion of immunoreactive cells for gonadotropins and alpha-subunit, in tumors characterized as null cell adenomas and oncocytomas, immunocytochemistry may provide valuable information to the pathologist and clinical endocrinologist contributing to the evaluation of this heterogeneous group of tumors.