Ovarian tumors with functioning stroma: a clinicopathologic study with special reference to serum estrogen level, stromal morphology, and aromatase expression.

Ovarian tumors with functioning stroma often show estrogenic manifestations. The range of serum estrogen level, however, has not been analyzed, nor the correlation with the stromal morphology. We reviewed the preoperative serum level of estradiol (E2) in 20 postmenopausal ovarian tumors that contained lutein- or theca-like cells in the stroma. Tumor histology included mucinous (n=7), endometrioid (n=4), clear (n=4), or Brenner tumor (n=2), carcinosarcoma (n=2), and Krukenberg tumor (n=1). Overall, the preoperative serum level of E2 ranged widely from 12.1 to 162.4 pg/mL (reference range, 10-30 pg/mL). The range of serum E2 was 24.9 to 162.4 pg/mL (mean, 58.0 pg/mL) in 7 tumors containing lutein-like cells, and 12.1 to 157.8 pg/mL (mean, 57.0 pg/mL) in 13 tumors containing theca-like cells alone. There was no significant difference in the serum E2 level between the 2 groups. To determine whether the functioning stroma is capable of final conversion of androgens to estrogens, the expression of P450 aromatase was examined immunohistochemically. P450 aromatase was exclusively expressed in the stromal cells, both lutein- and theca-like cells, in 16 tumors. In all tumors, however, it was focally or sparsely distributed, and there was no correlation between the immunoreactivity for P450 aromatase and the serum E2 level. These findings indicate that the functioning stroma, regardless of cell morphology, has a capacity for converting androgens to estrogens, but a significant amount of serum estrogens is finally qualified in the aromatase-rich peripheral tissues.