HORMONE PRODUCTION AND C-MYC PROTEIN LABELING IN PLURIHORMONAL PITUITARY-ADENOMAS

The biological activity of plurihormonal pituitary adenomas was compar ed with that of tumors producing only one hormone by evaluating the pe rcentage of c-myc protein-labeled cells and ultrastructural characteri stics. Twenty-five pituitary adenomas producing 3 or more hormones and 14 adenomas producing only 1 hormone were studied. Tissue sections we re stained immunohistochemically using antibodies for pituitary hormon es and c-myc protein. and they were examined by electronmicroscopy. DN A extracted from ethanol-fixed, paraffin-embedded tissue was analyzed for p53 mutations by polymerase chain reaction and single-strand confo rmation polymorphism analysis. The percentage of c-myc protein-labeled cells in adenomas producing 4 or 5 pituitary hormones was significant ly higher (p < 0.01) than in those producing 3 or 1 hormones. There we re no p53 mutations in plurihormonal adenomas. Pituitary adenomas prod ucing 4 or 5 pituitary hormones demonstrate biological aggressiveness; therefore, multihormone production reflects aggressive capacity rathe r than degree of differentiation.