DKK1 and metastatic malignant neoplasm in the lymph nodes: One of the two CpG islands that was not differentially methylated in the TCGA tumors overlaps the promoter region of DKK1, which has been reported to be hypermethylated in head and neck carcinoma [32, 33], and lower expression has been associated with increased risk of lymph node metastasis and poorer outcome [34, 35], although other studies report conflicting findings [36, 37].