The prognostic impact of cyclin D1 amplification or overexpression in unselected breast cancer has been inconsistent; 10 studies reported cyclin D1 expression to be a favorable prognostic marker [19, 25, 28, 32, 37–39, 41, 46, 49], 8 to be unfavorable [13, 14, 18, 26, 33, 34, 42, 44], and 21 studies found no association [7, 11, 12, 16, 17, 20–24, 27, 29–31, 35, 36, 40, 43, 45, 47, 48]. The gene discussed is CCND1; the disease is breast cancer.