A comparison of A103 and inhibin reactivity in adrenal cortical tumors: distinction from hepatocellular carcinoma and renal tumors

Distinguishing adrenal cortical neoplasms from either hepatocellular carcinomas or renal tumors can be difficult. Two recently described antibodies, A103 and inhibin A, are most often reported to be reactive with adrenal cortical neoplasms but with neither hepatocellular carcinoma nor renal cell carcinoma. To compare the sensitivity and specificity of these two antibodies in the diagnosis of adrenal cortical tumors, we stained 22 adrenal cortical adenomas, 4 adrenal cortical carcinomas, 25 hepatocellular carcinomas, and 43 renal tumors, including 33 renal cell carcinomas and 8 oncocytomas, with the A103 and inhibin A using an avidin-biotin complex technique. Fifteen (68%) of 22 adrenal adenomas and 2 (50%) of 4 adrenal cortical carcinomas were reactive with A103. Nineteen (86%) of 22 adrenal adenomas and 3 (75%) of 4 adrenal cortical carcinomas were reactive for inhibin A. None of the renal tumors or hepatocellular carcinomas reacted with A103, but 1 (4%) of 25 hepatocellular carcinomas (a high-grade pleomorphic tumor) and 1 (2%) of 43 renal tumors (a clear-cell renal cell carcinoma) were reactive with inhibin A. The cytoplasmic reactivity for A103 in adrenal tumors was coarsely granular and most common in clear-cell areas. Reactivity for inhibin was either cytoplasmic or membranous and stained both clear-cell and granular areas. We conclude that both antibodies are useful in the immunohistochemical diagnosis of adrenal cortical neoplasms and that A103 is slightly more specific and inhibin slightly more sensitive.