Previous studies have shown that high expression of CCND1 was associated with poor differentiation in oral squamous cell carcinoma, gastric cancer, laryngeal squamous cell carcinoma, and medulloblastoma or displayed no significant associations with cell differentiation in endometrial carcinoma.36, 37, 38, 39, 40 However, the level of CCND1 decreased with the increase in ccRCC grades. Here, CCND1 is linked to oral cavity squamous cell carcinoma.