Calretinin has been proposed as a novel marker of ovarian
sex cord-stromal tumors (SCST); this study aims to determine whether
calretinin can
complement or supplant the established utility of
inhibin in the differential diagnosis of SCST. WT1 has been shown to be expressed in ovarian serous, but not
mucinous neoplasms; its expression in a variety of ovarian
tumors is also examined.
Formalin-fixed,
paraffin-embedded archival tissues from 111 primary ovarian
tumors were analyzed with commercially available
antibodies using semi-automated immunohistochemistry. Results were graded on a 4-tiered scale with staining of more than 0 but less than 5% of cells considered focal. Of 27 SCST, 56% were
calretinin and 56%
inhibin positive overall; 90% of
granulosa cell tumors, 57% of
Sertoli-Leydig cell tumors, 33% of
thecomas, and 14% of
fibromas were
calretinin positive.
Inhibin was expressed in 60% of
granulosa cell tumors, 71% of
Sertoli-Leydig cell tumors, 43% of
fibromas, and 33% of
thecomas. Of 35 surface epithelial
tumors (SET), 8% of serous papillary
tumors were
calretinin positive, whereas 8% of serous papillary
tumors and 13% of poorly differentiated
carcinomas expressed
inhibin. WT1 was expressed in 29% of all
endometrioid carcinomas, 10% of borderline mucinous
tumors, and no
mucinous carcinomas; however, most of the other SETs were positive (77% serous papillary and 88% poorly differentiated
carcinomas). Among the SCST, WT1 stained only
granulosa cell tumors (75%), though often weakly or variably.
Calretinin has only slightly greater sensitivity (76% versus 65%) and equal specificity to
inhibin (92%) in the differential staining of granulosa or
Sertoli-Leydig cell tumors, that is, nonstromal SCST. Hence,
calretinin cannot replace but could
complement inhibin as part of an immunohistochemical panel used for diagnostically challenging SCST. Although WT1 should be reliably positive in non-mucinous SET, staining of
granulosa cell tumors and lack of expression in a sizable subset of
endometrioid carcinomas may confound interpretation.