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.