Yang et al. BMC Cancer 2010, 10:133 http://www.biomedcentral.com/1471-2407/10/133 Page 4 of 9 Figure 1 Immunohistochemical staining of Bmi-1 protein and Fluorescence in situ hybridization of Bmi-1 gene in human ovarian tissues. (A) Negative expression of Bmi-1 was observed in a normal surface epithelium of ovary (200×). (B) An ovarian cystadenoma showed low expression of Bmi-1, in which about 10% of tumor cells was detected moderate positive staining of Bmi-1 (200×). (C) Low expression of Bmi-1 was observed in an borderline ovarian tumors, in which 5% of tumor cells showed weak positive staining of Bmi-1 (200×). (D) Intensive expression of Bmi-1 was detected in an ovarian carcinoma (case 33), in which more than 90% of carcinoma cells showed strong positive staining of Bmi-1 (200×). (E) Another ovarian carcinoma (case 161) showed intensive expression of Bmi-1, in which all of tumor cells had strong positive staining of Bmi-1 (200×). (F) Amplification of Bmi-1 gene was observed by FISH in the same ovarian carcinoma case (161), in which Bmi-1 gene signals (red) was detected at least 3 times more than centromere signals of chromosome 10 (green) (1000×).