Calretinin,a more sensitive but less specific marker than alpha-inhibin for ovarian sex cord-stromal neoplasms: an immunohistochemical study of 215 cases

Although inhibin has been shown to be a sensitive marker for ovarian sex cord-stromal and fibrous neoplasms, it may be negative in some cases. Calretinin, a mesothelial marker, has shown promise as a marker for sex cord-stromal neoplasms. The aim of this study was to evaluate and compare calretinin and inhibin as immunohistochemical markers for sex cord-stromal and fibrous neoplasms. A total of 215 ovarian neoplasms were immunostained with commercially available antibodies to calretinin and inhibin. These tumors included 87 sex cord-stromal (39 granulosa cell, 13 Sertoli-Leydig, 4 Sertoli, 9 thecomas, 14 fibrothecomas, and 8 other stromal tumors), 37 fibrous (20 fibromas, 9 adenofibromas, and 8 fibrosarcomas), 65 epithelial, 22 germ cell, and 4 miscellaneous neoplasms. The staining was evaluated on a 0-4 scale based on percentage of neoplastic cells labeling: 0 = none; 1+ = 1-25%; 2+ = 26-50%; 3+ = 51-75%; 4+ = 76-100%. Calretinin reactivity was detected in 100% of sex cord-stromal and 90% of fibrous neoplasms, including 32 that were inhibin negative (2 granulosa cell tumors, 1 Sertoli-Leydig cell tumor, 1 thecoma, 3 fibrothecomas, 16 fibromas, 6 adenofibromas, and 3 fibrosarcomas). All four calretinin-negative fibrous neoplasms were inhibin negative. Calretinin staining was also detected in 22% of epithelial neoplasms but none of the germ cell and miscellaneous neoplasms tested. Inhibin staining was detected in 92% of sex cord-stromal neoplasms, 22% of fibrous neoplasms, 2% of epithelial neoplasms, and none of the germ cell and miscellaneous neoplasms tested. Calretinin has a 97% sensitivity and 85% specificity for sex cord-stromal and fibrous neoplasms, whereas inhibin has a 71% sensitivity and 99% specificity. This study shows that both calretinin and inhibin are useful in the diagnosis of ovarian sex cord-stromal and fibrous neoplasms. Calretinin is a more sensitive but less specific immunohistochemical marker than inhibin. Calretinin is particularly useful in the diagnosis of sex cord-stromal and fibrous neoplasms that are inhibin negative. The high frequency of calretinin in fibrous neoplasms suggests that a subgroup of these neoplasms may be derived from specialized gonadal stromal cells, perhaps thecal cells.