Comparison of Inhibin Alpha Subunit and Antimullerian Hormone Immunoreactivity in Granulosa Cell and Mucinous Ovarian Tumors

The inhibin alpha subunit protein is used in the histopathologic diagnosis of granulosa cell tumors (GCTs), and as a serum marker for disease progression. Yet, the availability of antibodies for inhibin has been limited. Serum antimullerian hormone (AMH) levels have also been described as a GCT marker. The goal of this study was to compare inhibin and AMH immunoreactivity in tissues and serum from GCT (n= 6) using existing and new antibodies. Expression was also explored in cases of mucinous tumors (n= 15), where inhibin is also a serum marker in some cases. Immunocytochemistry was performed using a commercial and newly developed inhibin alpha subunit and AMH antibodies. Serum levels were examined with total inhibin and AMH immunoassays. Inhibin alpha subunit and AMH were equivalent markers of GCT in both tissue and serum. In mucinous samples, inhibin alpha subunit was detected in tumor and stromal cells, and levels in serum were also frequently elevated. In contrast, AMH protein was detected in mucinous tissues, but there was no evidence of secretion in serum. The new inhibin alpha subunit and AMH antibodies provide needed resources for examination of granulosa cell and mucinous tumors.