CCNB1 and breast cancer: Increasing evidence demonstrates that CCNB1 is involved in checkpoint control, whose dysfunction is an early event in tumorigenesis, and that its deregulated expression is observed in a number of different human cancers including breast cancer, cervical cancer, lung cancer, esophageal squamous cell carcinoma, and melanoma (Kedinger et al., 2013; Kreis et al., 2010; Niméus‐Malmström et al., 2010; Nozoe et al., 2002; Yoshida, Tanaka, Mogi, Shitara, & Kuwano, 2004).