Diagnostic role of inhibin α-subunit and inhibin/activin β-subunit in adrenal cortical and medullary tumors in Egyptian patients

Inhibin and activins are dimeric glycoproteins that are structurally and functionally related to transforming growth factor-β and are composed of 1 α-subunit and 1 of 2 β-subunits (βA or βB). In recent years, there has been controversy about their role in adrenal tumors and their suitability as a diagnostic/predictive marker. Inhibin α and inhibin/activin β protein expression was assessed on 47 adrenal tissue specimens by means of immunohistochemistry. Positive immunoreactivity of inhibin-α was seen in all studied hyperplastic adrenal glands, 90.9% of cortical adenomas, and 83.3% of adrenal cortical carcinomas. In contrast, the adrenomedullary neoplasms had a statistically significantly different behavior (P=0.001). We observed the negative expression of inhibin α in 85% and 80% of benign and malignant pheochromocytomas, respectively. As regards the immunoreactivity of inhibin/activin β, 80% of adrenal hyperplasias, 81.8% of cortical adenomas, and 83.3% of adrenal cortical carcinomas showed positivity. Strong-to-weak positive staining of inhibin/activin β was observed in 70% of benign pheochromocytomas, whereas malignant pheochromocytomas showed positive immunohistochemical staining in 40% of cases with weak intensity. The scoring of inhibin/activin β immunoreactivity between adrenocortical and adrenomeullary neoplasia failed to reach the significant value (P=0.1). Our results demonstrate that inhibin α had a diagnostic role, differentiating between the adrenocortical and adrenomedullary neoplasms. Moreover, inhibin/activin β might play a predictive role for malignant potential in pheochromocytoma. Further studies are warranted to determine whether they play a diagnostic/predictive role in adrenal tumors or are just surrogate markers for this group of neoplasia.