CD44 and ovarian cancer: Many investigators have reported a group of cellular subsets similar to embryonic stem cells in ovarian cancer tissue samples that markedly express markers such as CD44, CD133, and c-Kit (CD117); and that possess stem-cell “stemness.” However, these cells also portray the characteristics of highly proliferative, invasive, and tumorigenic capabilities inherent totumor cells, such that they are referred to as ovarian cancer tumor stem cells (OCSCs) 3-5.