A clinicopathological and immunohistochemical study of clinically non-functioning pituitary adenomas: A single institutional experience

Background : Non-functioning pituitary adenomas (NFPA) are characterized by the lack of clinical syndrome as compared to functioning adenomas (FA) but not all functioning adenomas have clinical effects. Their exact incidence varies in different series.
Materials and Methods : This study was undertaken to analyze the hormonal profile of NFPA at the immunohistochemical level in the Indian population and to see if any differences exist from the earlier studies. Their biological aggressiveness was also studied by MIB-1 labeling index (MIB-! LI) and Epidermal Growth Factor Receptor (EGFR) expression. These parameters along with their clinical behavior were correlated with radiological features of invasiveness and size.
Results : Of the 151 pituitary adenomas diagnosed during a period of one and half years, 77 (51%) were NFPA with a male predominance. There was increase in the incidence of NFPA with increase in age. Immunopositivity for various hormones was observed in 64 (83%) cases, either singly or in various combinations. On the basis of immunohistochemistry, NFPA were classified into three subtypes; gonadotroph adenomas, silent adenomas, and null cell adenomas. Gonadotroph adenomas were the commonest subtype. In general, NFPA showed low MIB-1LI but invasive NFPA had LI on the higher side, however, this difference was not significant. We observed EGFR positivity in two cases only; therefore the tumorigenesis mechanism may be different in NFPA.
Conclusion : Although non-functional at the clinical level immunohistochemistry showed reactivity for various hormones. If a battery of immunostains including seven hormones is studied, a significant number of cases are shifted to the functional group.

Keywords
Immunohistochemistry, neoplasia, non-functional adenomas, pituitary adenoma, pituitary gland, sellar tumors