We detected hypermethylated ctDNA in 22% (ZNF660), 26% (CCDC181), 31% (ST6GALNAC3), and 44% (HAPLN3) of the patients with PC (Table 5 and Fig. 3A,B), whereas all serum samples from patients with BPH were negative for all four genes (i.e., corresponding to 100% specificity and 22–44% sensitivity for PC). Here, ZNF660 is linked to pachyonychia congenita.