CDKN2A and renal cell carcinoma: Subgroup analyses based on sample types showed that p16INK4A promoter methylation was significantly associated with RCC risk in tissue (OR = 2.82, 95% CI = 1.61-4.95, P < 0.001), but not in serum or urine (OR = 1.66, 95% CI = 0.66-4.16, P = 0.28; OR = 15.82, 95% CI = 0.41-608.03, P = 0.138, respectively).