Expression of P450 Aromatase in Granulosa Cell Tumors and Sertoli-Stromal Cell Tumors of the Ovary: Which Cells Are Responsible for Estrogenesis?

Granulosa cell tumors are representative of estrogenic ovarian tumors, and some Sertoli-stromal cell tumors are also estrogenic. The exact cells that are responsible for estrogenesis, however, have yet to be identified. In the present study, 25 sex cord-stromal tumors (20 granulosa cell tumors, 4 Sertoli-Leydig cell tumors, and a Sertoli cell tumor) were immunohistochemically examined for expression of P450 aromatase, which is critical for estrogenesis. All of the tumors had been evaluated for estrogenic function, including contemporaneous endometrial hyperplasia and/or elevation of serum estradiol. Eleven of 14 estrogenic granulosa cell tumors showed sparse or aggregated immunoreactivity for aromatase, whereas 5 of 6 nonestrogenic tumors did not. Aromatase was selectively expressed by plump granulosa cells with eosinophilic or vacuolated cytoplasm, resembling luteinized granulosa cells. Such a localization of aromatase is analogous to that in normal ovaries. Aromatase expression in primary tumors was recapitulated by recurrent tumors. In Sertoli-stromal cell tumors, either undifferentiated plump cells or well-differentiated Sertoli cells expressed aromatase. In conclusion, the expression of P450 aromatase corresponds to specific cell morphology in sex cord-stromal tumors, including recurrent tumors. Aromatase status in granulosa cell tumors provides helpful information on whether serum estradiol could be a marker for recurrence.