PCDH17 and neoplasm: PCDH17 was more methylated in case than in controls and methylation in serum was correlated with advanced stage, higher grade, lymph node metastasis and tumor progression. In addition, patients with methylated PCDH17 had shorter progression-free survival and overall survival than patients without, and methylation in serum was an independent prognostic factor for worse progression-free survival and overall survival of patients.