CDKN2A and neoplasm: As a whole, tumors were more highly methylated than adjacent normal tissues at both exon 1 and exon 2 regions with statistical significance as shown in Fig. 4c, namely p16 exon 1 adjacent versus tumor (t = 6.579, p < 0.01) and p16 exon 2 adjacent versus tumor (t = 11.543, p < 0.01).