Fischer AF, Pham DL, Bösmüller H, et al. - In this study, 215 serous ovarian tumors [high-grade serous carcinomas (HGSC, n = 161), low-grade serous carcinomas (LGSC, n = 17), atypical proliferative serous tumors (APST, n = 37)], and ten cases of serous tubal intraepithelial carcinoma (STIC) were investigated in order to contrast the expression and co-expression of stem cell markers ALDH1 and SOX2 in various types of serous ovarian tumors. It was discovered that co-expression of ALDH1 and SOX2 or ALDH1 and Ki67 had no impact on survival. In comparison with low-grade carcinomas and borderline tumors, expression of stem cell factors ALDH1 and/or SOX2 exhibited raised frequency in high-grade serous ovarian carcinomas suggesting the concept that stem cell markers play various biological parts in low-grade compared with high-grade serous neoplasia of the ovary.