Progressive loss of selenium-binding protein 1 expression correlates with increasing epithelial proliferation and papillary complexity in ovarian serous borderline tumor and low-grade serous carcinoma.

Ovarian serous borderline tumor, micropapillary serous borderline tumor, and low-grade serous carcinoma often show a spectrum of histologic components with increasing epithelial proliferation and papillary complexity from flat cyst wall, hierarchical structures (with primary papillae branching into secondary papillae), micropapillae, and invasive carcinoma. Although tremendous research has been carried out to elucidate the causes of these tumors, the pathogenesis remains unclear. Literature has described a relationship between insufficient selenium intake and increased risk of cancer. The anticancer action of selenium has been suggested to be mediated by selenium-binding protein 1 as selenium-binding protein 1 is decreased in several cancers. The aim of the study was to examine by immunohistochemistry the expression of selenium-binding protein 1 in the various histologic components within ovarian serous borderline tumor, micropapillary serous borderline tumor, and low-grade serous carcinoma. Our study consisted of 62 cases of ovarian serous borderline tumor, 11 of micropapillary serous borderline tumor, and 7 of low-grade serous carcinoma. Review of archival slides showed flat cyst wall in 69 cases, primary and secondary papillae of hierarchical structures in 75 cases, micropapillae in 26 cases, microinvasion in 1 case, and frankly invasive carcinoma in 7 cases. The strongest immunoreactivity of selenium-binding protein 1 was seen in epithelial cells of flat cyst wall and primary papillae, followed by secondary papillae of the hierarchical structures. Micropapillae and invasive carcinoma (including microinvasion) exhibited a near complete loss of selenium-binding protein 1 expression. Selenium-binding protein 1 immunoreactivity remained the same regardless of the size of the micropapillae. Similar selenium-binding protein 1 expression was seen in the same histologic components from either ovarian serous borderline tumor or micropapillary serous borderline tumor. The gradual loss of selenium-binding protein 1 associated with increasing epithelial proliferation and papillary complexity indicates that selenium-binding protein 1 is involved in tumorigenesis of ovarian serous borderline tumor, micropapillary serous borderline tumor, and low-grade serous carcinoma. Our findings may provide a basis for future studies concerning the molecular mechanisms of selenium-binding protein 1 in tumorigenesis as well as a possible role of selenium in chemoprevention and treatment of ovarian serous borderline tumor, micropapillary serous borderline tumor, and low-grade serous carcinoma.