Expression analysis of Bmi-1 protein by immunohistochemistry. Bmi-1 staining was mainly localized within the nuclei, and it expressed was observed in cancer cell. A: Negative Bmi-1 staining in non-cancerous tissue (100×). B: Weak Bmi-1 staining in non-cancerous cells(400×). C: strong Bmi-1 staining in tumor nests(400×). D: Strong nuclear stainingin most of the tumor cells (400×).