PCDH17 and pachyonychia congenita: Methylation could occur in PCDH8, PCDH10, and PCDH17 in both PC tumor tissue and serum, and is associated with poor prognosis and shorter biochemical relapse-free survival (Losi et al., 2011; Lin et al., 2014; Viu et al., 2014; Wang et al., 2014; Lin et al., 2015; Lin et al., 2017).