Wang QS, et al. - The prognostic roles of Cyclin-D1 (CCND1) in clear cell renal cell carcinoma (ccRCC) were investigated for the first time in this study by using Gene Expression Omnibus database, The Cancer Genome Atlas database, and immunohistochemical staining. In ccRCC tumor tissues, significantly enhanced mRNA and protein levels of CCND1 were evident. Poor prognosis and tumor recurrence were observed in relation to low level of CCND1, but not high level of CCND1. With increasing ccRCC tumor grades and the rate of recurrence, reduced CCND1 mRNA levels were detected. For recurrence prediction, CCND1 was identified as a strong determinant. More favorable prognosis together with more frequent low-grade tumors and low rate of recurrence was seen in cases with high CCND1 level. An unconventional positive influence of CCND1 on the clinical outcome was shown in ccRCC patients.