The alpha subunit of inhibin in adrenal cortical neoplasia.

We analyzed 23 adrenal adenomas and 15 adrenal cortical carcinomas by immunolabeling for the alpha subunit of inhibin, and we then compared the results with the functional status of the neoplasms. We also studied 19 pheochromocytomas, 30 renal cell carcinomas, and 5 extra-adrenal paragangliomas, tumors posing differential diagnostic problems with adrenal cortical neoplasms. Immunolabeling was performed using automated immunohistochemical methods and an antibody directed against the alpha subunit. Tumors were semiquantitatively assessed for the number of positive cells. Immunopositivity was obtained in 18 (78%) of 23 adrenal cortical adenomas, 12 (80%) of 15 adrenal cortical carcinomas, 2 (11%) of 19 pheochromocytomas, 0 of 5 extra-adrenal paragangliomas, and 0 of 30 renal cell carcinomas. Immunoreactivity was strong in 7 (78%) of 9 adrenal cortical tumors from patients with Cushing's-related or virilizing symptoms. In contrast, only 4 (14%) of 29 tumors that were clinically nonfunctioning or associated with hyperaldosteronism demonstrated strong staining (P < .001). In clinically nonfunctioning tumors, there was a tendency for increased immunopositivity in tumors from patients with elevated levels of cortisol, androgen, or their precursors, with four of six tumors having at least moderate immunopositivity. Similar reactivity was present in only one of eight tumors from patients with normal laboratory values (P=.091). Moderate or strong immunopositivity was present in 9 (60%) of 15 adrenal cortical carcinomas, whereas of the pheochromocytomas, extra-adrenal paragangliomas, and renal cell carcinomas, only 1 (1.9%) of 54 showed moderate-to-strong reactivity. We conclude that moderate or strong immunoreactivity for the alpha subunit of inhibin occurs in adrenal cortical tumors from patients with Cushing's-related or virilizing symptoms. Immunolabeling for the inhibin alpha subunit is potentially useful in the differential diagnosis of neoplasms that include adrenal cortical carcinomas.